Carbon tool steel should work for you. You only need high speed steel if will get hot enough to lose the temper. If it needs sharpening, that can happen pretty easy on a grinder…but for a prototype, you just need to take care not to overheat it.
If I was making it, I’d use O1 tool steel. Readily available as drill rod. You can buy 3’ lengths of 1/2" diameter for $10 or thereabouts. (been a while, so it might be more these days). McMaster-Carr or MSC will have it. If you have a Metal Supermarkets franchise in your area, you can probably buy it by the inch.
It comes annealed, and machines like mild steel. (actually a little better, it isn’t as “gummy” as 1018) BUT you must keep it cool with cutting oil or other machining coolant. If you let it get hot in a small area, the remaining mass can quench and harden small areas. Goes double for welding.
Work outdoors. You could well start a fire. Have a fire extinguisher handy…dry chemical, NOT water! A grease fire is not unlikely. Be careful.
Fill an old can half full of used motor oil or similar. Place this in pie pan or similar full of sand (fire/spill precaution).
Use a torch (propane will work for small items) and heat to a dull cherry red. Test with a magnet, if it is still magnetic it is not hot enough. It needs to be a bit hotter than where the magnetism is lost.
Drop it into the oil bath. Expect the oil to catch on fire. Place a lid over the can to put the fire out.
The item is now full-hard. Test it with a file…the file should slip without biting into the steel. This will shatter in your use, so you need to temper the item.
Polish the item with emory paper, steel wool, scotchbright, etc. You need to get all the scale and burned oil off from the quenching operation.
Working in good light, but in the shade, heat the item untill oxide colors appear. You probably want somewhere between light straw and dark brown. For your item it may be easier to place it in a pan of sand, and heat it on the stove.
Quick and dirty tempering method I have used for non cutting tools (hardened washers, custom bolts, and the like). Don’t bother polishing the item. Place it in a shallow pan (I usually use a jar lid, or the dished bottom of an aluminum beer can). Put about 1/4" of used motor oil in the pan. Play a torch on the oil until it starts burning. Keep the torch flame off the part. Get it to where the oil it will stay lit without the torch. Let it burn untill the oil all burns.
There is a lot of data on heat treating O1 online. The tempering is pretty much the same for Oil, Water, and Air hardening steels. O-1 is the cheapest, and the oil quenching isn’t really that much of an inconvienience.