I won an ATV cover at one of those benefit auctions we did to raise money for a friend who needed money to cover the costs of cancer treatment.
It fits the whole bike, is waterproof except where moisture might blow up under it in spots, has an elastic band in the edge which makes it fit pretty tight around the bike, the only down side was it is some kind of woodsy camo, although I like that sort of thing anyway...lol. It fits from under the front of the front fender all the way back over the rear trunk and saddle bags, and down the sides all the way to the exhaust pipes.
And it wads up into a very small ball that fits way back in one of the corners of my saddle bag.
Might look at something like that. Not specifically made for a MC but it sure works for me.
Mac