One option to keep in mind is buying new. They sell the cage in sections, so if you don't need everything you could buy just the sections needed.
Agree with the above regarding models that interchange, but probably won't be easy finding a used cage for this machine. I've regularly searched for Teryx related parts on many sites and have only come across maybe one or two used cages that were reasonably close enough to pick up (shipping would be a killer on these). The fact that it is a 2 seat probably won't help either as there just not as many of those either. Not saying they are not out there but most used stock cages I see are from people putting custom cages on...and simply not that big of market for doing that with a Teryx.