I don't know if this is exactly what you're looking for since it's a universal cheap cover but I've had good luck with my Harbor Master cover that I got from Wal Mart for something like 50 or 60 bucks. It's trailerable with a couple quick bungees, super light, packs down really small so it would be easy to keep in the truck. It keeps my boat covered, actually fits decently well, I can't complain. I think it even has a few years warranty. I didn't find it too bad for the price. It definitely does the job, how bout that. They make it in a few sizes, 17-18, 19-20, and like 21+ or something like that.
Triton Tr20 - 225 Optimax
Bullet 20DC - Merc 2.5