Here's a link to some nice enclosed trailers.
I agree with Wry, Floe makes great open trailers, I think they also make covered trailers.
I was just at a trailer place today picking up brake components for my Karavan trailer(not so good trailer), they recommended Floe and Wells Cargo. Wells has a real nice Aluminum 25' for a mere $9895.00 list price. Wow. Nice enough to live in(which is what I'd have to do if I bought it, my wife would make me). Seriously a few things to look for, frame size, floor support spacing, tire size, plywood thickness.
Good luck
http://johnstrailersales.com/snowmobile_trailers.html
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