Good day dears, I'm from Russia, and have good expiriance in question of selfmade belts.
for prepairing og this you need some equipment:
1 - wooden plate
2 a piеce a good quality rubber with thik as you need
3 rubber qlue
4 carpentry machine or drill/
when you will fix with clue the rubber, use the bolt int he center of plate with clued rubber
if you use machine, just cut 2 rings, as you need, if dreel, be carefull, fix dreel and cut by sharpen knife