My MIL has a few of those at home as well. FIL got quite a kick out of them.
I get mine at trade shows. You can enter without registering if you come late in the day. Usually they won’t be manning the doors, or they will accept your statement that you are returning from lunch and left your badge inside. Or you’ll see a few badges tossed just in the wastebaskets. Trade shows are less fun than wedding crashing, but you can get all the pens, magnets, and key fobs anyone can use 
You may find that it’s not the pens, but the paper. In my experience that paper that’s used to print out your credit card slip that you sign is ultra smooth and even cheap pens provide a great feel. Take that pen home and write on regular paper and you’ll find it’s no better than any other.
You might want to try browsing American Science and Surplus. No guarantees that they’ll have what you want in stock at the moment, but their inventory changes rapidly. I must warn you, though, that this site is dangerous to your credit card. Every time I visit it, I find things that I never knew existed, but my life will be incomplete without these things.
Not only that but American Science and Surplus’s catalog is a hoot to read.
You know, some dudes collect those pens.
Related to the op,
I once found the best hilighter I have ever used. It was just lying on the floor from a previous class. I picked it up, and started using it. Thankfully, Bic left their name on it, even after it was promtionally imprinted.
A quick google to Bic, and then a click on Bic’s visual catalog showed me the exact hilighter I had (sans imprinting, obviously).
Here is the best part, Dollar Tree consistently has the same ‘brite liner’ highlighters 3 for a dollar. (pre packaged, pink blue yellow).
I’m on the fence about going in bulk for pencils and pens for personal use. Then again, Im good on pencils right now.
The one thing I miss about working as a medical secretary is the pens. Once, a drug rep gave each of the secretaries in my office a very nice, heavy, refillable Remicade pen. It was a fantastic pen. My favorite pen ever. Alas, my desk was positioned in the middle of the office right next to an open area with some filing cabinets where the doctors tended to congregate, and thus, I had pen theft issues. I managed to hold on to the glorious Remicade pen for half a day. I even put it away in a drawer when I left for lunch. I came back half an hour later, and it was gone. The drug rep was gone too, so I couldn’t get another. To this day, I mourn the loss of that pen.
After that, I procured a pen with bright purple sparkly ink. Nobody stole it for a whole week.
Oh, I feel your pain. I hate pen thieves. Eventually, I got crafty on the buggers. Literally.
I took a small, never used plant pot and filled it with coffee beans. Then I took some silk daisies, cut most of the stem off (leaving about a two inch stem) and hot glued them onto some of my favorite gel pens. Then wrapped the stem and body of the pen with green florist’s tape. Stuck the pen flowers in the coffee beans so they’d stand up, and it looked like a potted plant. Took me about 15 minutes to do a dozen flowers. Very cute on my desk, and I always knew who stole my pens, because they had daisies on the end! 
(And the coffee beans are a natural deodorizer and air freshener, which is a bonus in most offices.)
I actually seem to collect more pens than I lose. After every class, it seems like I’m retrieving a pen or two that some student left behind. They all go into a can, to be loaned to those students who left their pen in their last class.
I’m usually up three or four pens a week.