would be easier if your hobby was fishing. I bought a cover for my bike's drivetrain but I couldn't figure out how to put it on & it tore in the process. now I cover those parts w/ plastic bags & velcro straps & tape. I like this saddle cover tho
Brooks England Nylon Saddle Rain Cover

this one was OK, but wasn't 100% waterproof, so not good for leather saddles. also it degraded over time. I often use it under the Brooks cover, cuz, why not
Serfas Waterproof Seat Cover

maybe this will work for you. probably smarter than me ;-)
M-Wave Bicycle Chain Guard Cover