Or a variation on the theme is to have the load suspended in the center of the pole and the two ladies carrying one end each. A broomstick or mop handle would work.
This type of hand cart works well on stairs, but you still have to pull it up. It may allow 2 people to pull it together if the stairway is wide enough.
p.s. This is the one I got recently after I hurt my back. It should be more than sufficient for a 20-lb box. But I haven’t tried to lift it with 2 people so I don’t know if that’s an option.
These days? Are people more likely to murder someone instead of helping them with cat litter than they were in the past? 
You could wrap the cat litter in a FedEx package and call for pickup. Have it addressed to the apartment and marked for inside delivery!
Or you could use a 1-person Moving Strap. You can Google to find a brand that you like. I read one that says: “These furniture moving belt straps for one person are made to hold up to 550 pounds.” But, as it also says: “[Warm Tips]- Before using our moving lifting straps for moving heavy objects, please make sure the weights of them within your operational limit and keep balance. If not, maybe will be getting hurt yourself and breaking your moving things.” That’s a good warm tip! It really hurts when I break my moving things!
This is exactly what I’m thinking. Put the litter box on the first floor. But she probably can’t install a cat door.
And BTW, a container of light litter weighs much less than 20 lbs., but is a bit more expensive than regular litter. I used it for months, after my heart surgery.
One of my apartments in NYC was in a 5-floor building with no elevator. It was in a part of SOHO that had been part of Little Italy. All the people on the 5th floor were elderly Italians who had to schlep their groceries (including cat litter) up all those stairs. Somehow they managed.
Because they don’t sell lightweight litter in 20 lb quantities.
Actually I didn’t know that, but I checks and it appears to be true.
This assumes that (A) the landlord will allow a litter box in a public space on the first floor, and (B) the landlord will provide storage space on the first floor for her to keep the boxes of litter. Both of those assumptions seem unlikely to me.
Wouldn’t a bedpan have been easier?
sorry
As to the OP, knock on your neighbor’s doors and look cute. It worked for my 97 year old mother in law - she got people to pump her gas, carry her groceries, Heaven knows what else.
Regards,
Shodan
Ask the landlord to install an Einstein-Rosen bridge.
It might be slightly cheaper to fix the elevator.
Or (C) how thrilled the other tenants will be passing by someone else’s pet’s organic leavings every time they leave the building or (D) why there would not be a dozen cat boxes in the lobby after a while.
So is the OP ever going to return to let us know how she resolved the issue? Or is she still climbing those steps weeks later?
Look-if there is supposed to be a working elevator then insist that the landlord FIX THE DAMN THING!! I’d bet it’s illegal to let it set in a broken state. First call the city and ask who can tell you what the law says. I’d say it’s implied that you will have a working elevator if it’s there. Why on Earth wouldn’t you demand it get fixed?
We buy the 40 pound containers and the delivery person brings it to the front door, no extra charge.
How does the neighbor get it from the shelf to the car?
This is brilliant and I second this approach. If you do, please upload the video to YouTube and post a link.
OP has heart problems. I don’t think your heart cares whether you’re carrying the extra weight in your hands or on your back.
That’s assuming your potential helper is right there, right then, and has nothing better to do at that moment.
Otherwise, $10: $5 for the carrying, and $5 for making them come from somewhere else, or getting them to be there at some other time, or pulling them away from what they were doing instead.
Hell, $10 to get their attention - $5 just isn’t much these days.
Someone mentioned using pulleys /block and tackle.
How about another simple machine – an inclined plane? You probably don’t have a board long enough to complete a flight of stairs sliding the bag on the board
Instead, as long as the board is long enough to reach ~4 stairs, you could slide the board and bag up the stairs as one unit.
(though I think breaking the bag into smaller units is the best solution)
Brian
Oh, you’re no fun.
Regards,
Shodan
All these wacky ideas…and nobody’s mentioned a hand truck? Good lord.
I remember working as a maintenance worker and being assigned to a building that was being renovated as a charter school that was renting space in a church. It was a 3 floor building and the only elevator only went up from the basement to the main church floor (the sanctuary) so we had to bring heavy (and I mean heavy!) furniture that was being moved to the office space on the third floor by hand. We used hand trucks, with two, or sometimes even three people pulling the handtruck, to roll them up several flights of stairs. There was also a lot of furniture so it took a whole shift. Oh yeah, it was also during a hot day and the building had no AC. Needless to say, it was not fun.
A 20 lb box is nothing in comparison and I’m sitting here laughing at all these crazy ideas you guys are posting for such a thing.
So yeah, hand truck.
Um, no.
A hand truck itself weighs more than 20 lbs.
These tiny women can’t handle both the truck and the load.