There are several belting suppliers in Seattle, and a couple more in Tacoma. They will usually punch them for you. So far all the belting / Tracks, that I have purchased from the Conveyor suppliers have been from one half, to one eight of the price and the belting was as good or better than the factory stuff.
Do NOT use an old belt as a template to punch out a new belt. The old one is streched and the irregular or incorrect spacing will lead to high sprocket wear and detracking.
Most of the Belting suppliers are selling long conveyors, often miles long, and have Scraps, or "Rems" (remenants), that are great for a track vehicle that only needs 20 foot of belting. They are more than glad to sell the shorty pieces that they would normally be throwing out.