I actually just bought a cover for mine.. the driving reason behind it was its being stored in a farm shed over the summer so to keep dust and bird poop off the actual bike after cleaning it so well.. I could have gone with a cheaper one (Royal had them in their tent sale for about 20 bucks) but was concerned about fit, and figured I wanted one for trailering to keep the salt off as well.
I have a Polaris X2 which has the dump box on the back instead of a rack. So I went OEM and paid through the nose but got the one that's trailerable as well. My only other option was from EBay, but after reading the feedback from some, decided against them.
I didnt try it with the windshield but it didnt look like it would fit very well.. maybe I'll try in the fall.. my windshield is a quick connect/release so not the end of the world.