[shawn1231]

We encountered the same problem. We ended up using a Poly-Cord belt for to drive our shooter. We found pulleys at the hardware store but they only came in 1/2" and up. So we started looking around and found a shaft collar/bushing that is about 1 1/2" long and has two large set screws. It just so happens that this 5/16" collar fit the 8mm shaft and that it was exactly 5/8" in diameter. So we bought a pulley to fit the 5/8" bushing.

I don't know about a keyway though. We were able to do it without one simply because our pulley had a gigantic set screw and our bushing has two. If you find that a keyway is not necessary though, definitely try poking around the hardware store just to see what you can stumble across.