I got one of the Bilt covers on sale from Cycle Gear. It was about 1/2-price. I also have a Dowco for another bike which is also a good one. I think they have different qualities, I think the one I have is a upper-level, it's held-up well for a couple of years.
Addendum: I checked and mine is also the Dowco Guardian, a very satisfactory product.
I saw a guy selling a CL offering & he said it was a H-D, $200 supposed cost & when I went to see it, I wouldn't have paid $25 for it. it was a nylon taffeta unlined dust cover, very thin, a waste of time. Caveat emptor!