1024 used belt this year for their elevator. We joined our belt together by lasering out (you could Plasma or CNC too) a pair of brackets with rectangular cutouts through which the teeth on the belt would fit. Then, these plates, two per side for each end of the belt, were tightened down on the backside of the mounting plate for our gripper. The clamping force was plenty, and the belts never slipped all season.
If you need more details on that, let me know.
For a source of very long timing (synchronous or cog) belts, we used
McMaster Carr (just search "Synchronous Belts"). For an XL pitch (just for an example) 1/2" wide belt it's $2.59/foot, and if remember right (you'll want to call on this b/c I cant remember exaclty) the maximum length was 30' (might have been 50' can't remember, sorry
)
SDP-SI is a good source too, but not as cheap for belt. However, they do have better deals for pulleys.
Well... eh... thats all for now.
-q