There are a BUNCH of things to consider when look at replacing the belt with another one. Here's but a few:
overall length
Vee angle
Type of facing
Cord style/type/construction
width
cogged vs non cogged
distance between internal cogs
distance between external cogs
temperature resistance (and airflow that is generated by the belt, if applicable)
All those (and more) are specifically chosen by the manufacturer for the type machinery that the belt will be used on.
I worked on a lot of Kawasaki Mules and Teryxs and ATV's (Prairies/Brute force/etc). What I learned, belt adjustment is critical and so is the OEM belt. Dayco belts never lasted as long as OEM. Neither did SuperAtv belts or Highlifter or any other aftermarket. Secondly they never performed as well as OEM. Aftermarket belts are almost always less expensive but that in itself makes me question where did they cut a cost? Material? Construction? They never tell you that. Yamaha belts vs Dayco, same deal. OEM always outperforms the aftermarket "replacements"-100% of the time.
You might be able to find one but you'll be wise to ask an expert in the field of V- belts to measure and inspect your OE belt and then come up with something for you. Maybe they can, maybe they can't.
And it may not have any bearing on the OP's issue, but I felt it a good time to discuss how the CVT's work on all CVT equipped machines with the exception of Yamaha (and the Teryx 800). When you mash the throttle pedal, the primary clutch closes up onto the belt. It basically pinches it between the two sheaves. If you are in high gear and the wheels ain't moving, or moving very slowly, you are slipping the primary sheaves on the belt. This creates heat. The longer you sit there the more slippage and heat is generated, thus belt and sheave wear. For this reason alone, it is highly advisable to be in LOW gear when under about 10 mph, like, say checking fences, spraying, etc---and also ANYTIME there is a load behind it, such as a trailer, pull behind shredder, etc. These CVT's are nothing like an automatic transmission in a car, you can't just sit there with your foot on the floor with the wheels not turning and expect something to happen at some point. You'll smoke the belt and possibly damage the primary clutch. The Teryx 1000, all of the Kawasaki Mules, their ATV's, Polaris (all), Can-Am, they all use the same basic design. Yamaha (and the kawi teryx 800) both use a wet clutch to drive the primary sheave assembly. In doing this the belt has constant tension and there is no slippage. Yamaha is so confident in their design that they put a real warranty on their drive belts. In 30 years of Yamaha dealings I think I replaced 2 yamaha belts. Also, because of the design of the Yamaha setup, you can actually have GREAT engine breaking, and it's so good that you can push start one. No other manufacturer can lay claim to that. In 2 years of Polaris, I put that many belts on in the first 2 days of working there. But again education in how the system works and then correcting usage mistakes will almost always extend CVT life dramatically regardless of whose system is being used. Little video below to see how the systems work: