Since your seat is there can you call and ask it they can make a seat cover? If so can you see what they charge?
This may be a good deal for them; if they're advertise that they can make them they will be able to sell them. I couldn't find anything on their website about removeable seat covers or rain covers but they have to know there's a market for them.
Retired USAF, IYAAYAS!
2008 V-Star 1100 Custom Bobber project
2011 Crimson XR with Forged Highway Bars / Hard Bags / Passenger Backrest, Ness parts including Smooth Layback Plate Frame/Mount / Rad 3 Mirror / deep cut grips / drivers floorboards /shifter peg / brake peg / passenger pegs. Witchdoctor black rack, Lloydz filter / timing wheel / VFC III, 7Jurock windshield, Drag Specialties seat.