Almost anything but an MCI. I'm not sure what you want to use the ATV for, but Yamaha made a 125 (Breeze) that would even fit into an MCI bay. A Rancher is a big unit..the 4X4 is taller yet. Still, as long as it's backed in, it would go in most coaches other than an MCI. You can get upwards to 700 CC in the same sized package (Kawasaki Prairie 700)..
A Yamaha Breeze is a low item. It isn't a good rough off road item, but good for moving one person around where a bus would usually be found. Yamaha built a better looking version of the Breeze in a "Grizzly" 125. Same thing..just better looking, and due to the high-tech looking plastic, a little higher at the rear.
If you plan to use the thing in campgrounds, be careful...most campgrounds don't allow any gas powered toys. I just bought an electric Club Car golf cart for that reason..wanted a Yamaha Rhino (I sell Rhinos), but when checking with several campgrounds, they wouldn't allow it. Even with my "handicapped" placard...which I borrowed from my sister in law!
HOWEVER, I was recently in one of those campgrounds that don't allow gas powered toys and there were gas powered golf carts zipping all over. I feel downright geriatric in my silly slow golf cart. Need a big motor, lift kit, wheels/tires....we'll get there~
BTW, if you want any dimensions off of a Kaw, Yamaha, or Suzuki, let me know and I'll measure and post whatever you want to know. Not a Honda dealer so can't help much with that.
Cheers, JR