I do a fair amount of such things.

Any good farm supply store should have a full rack of hubs, weldable
sprockets, weldable pulleys, chain, V belts, and pillow blocks. If you
need an odd shaft size with an even odder tooth count, this is the way
to go. Pick a hub, pick a sprocket, weld it up. These will be stock #35,
#40, #50 chain, 3L, 4L, and 5L 'V' belt. Not good for high speed or high
loads but nifty. They also should stock the funny chain used for making
conveyer assemblies. Stamped links, about 2" on center. Tractor Supply,
Fleet Farm, Fleet and Farm, etc.

I had to get an account a Grainger because they seemed to be the only
folks who handled motors, 4 step pulleys, and such.

McMaster is where I usually get things like LoveJoy couplers, set
screws, inserts, etc.

SteveB wrote:
I want to make some different contraptions. I need some chain, sprockets,
drive motors, vee pulleys, pulleys, etc. Something to make low rpm turning
devices.

What is a good supply parts house for such things?

Steve