Truck maker, thanks for the link. I always forget about McM for parts. I just seem to get stuff other places.
Tom, the .25 looks okay. Maybe just a bit big but not too bad. The common 10T sprocket would even look okay next to the tumbler but I might have to search for a smaller one on the motor.
The little pulley I have in the photo is about the size of the smallest sprocket I have found so far.
Jim