I use a Harley brand cover, I like it. The one I use is for indoor storage. You have to choose between an indoor or one that is for outdoors. Storage cover, rain cover, dust cover, sunblock cover, packable cover, one with heat sheilds, etc., etc.,
I went to valueaccessories.com and got one of their XL touring bike covers. Good price and they come in a packable bag so you can just stuff it into your bag when not in use.
I got a Nelson-Rigg from their website. I believe the price as around $75. The cover is made well, waterproof, and vented. It will cover the back with or without a passenger backrest,. The windshield area has a soft protective lining, and the bottom is supposed to be heat resistant. I had mine about a month and I burned a hole in it. I think the pipes were a little too hot to put the cover back on. I called the company, they apologized and sent me a new cover within 3 days. Have had no other problems with this cover.