DIY Conveyor Belt (with Pictures)
A neater design would be to use a small length of some hollow metal 8mm tube as a support guide with the shaft of a NEMA 17 though the middle to a rubber bung. This would avoid the use of other cogs and belts. Your stepper can probably drive your belt way faster than you need, so using a large drive cog from a small stepper cog is an advantage.