I could not find a conveyor belt that I could just download and print so I designed one myself. As you can probably tell it is heavily inspired by RC Tank Tracks. I did use a model for the 28byj48 stepper holder from thingiverse and modified it to suit my needs, however I got no clue who it was so I can't give credit unfortunately (otherwise I would have).
All of the bolts are M3 and most likely 30mm long. Each of the "belts" are connected via 1.75 pla filament. Probably ok for short runs but if your belt is going to get really long = get metal ones.
The entire contraption works just fine but I am sure that there is room for improvement!
I did make a video of this working (Arduino controlling the stepper and moving the belts) and posted it on my twitter account. Not sure if this is allowed on this platform but will leave the link: