Ever look for "real" saddlebags? Just gotta shorten the center "strap" some. Easy enough with a hole punch and latigo lacing. Same with securing the bags to the rear rack. The bags can be found used and new ones can cost way less than motorcycle saddle bags. I've even seen them for sale out here. You wouldn't think it, but we do have working ranches on most of the islands.
Btw, try checking places like Cabela's or any of those big name hunting/fishing suppy stores. I recall seeing saddle bags for sale in some of their catalogs. Plain and simple, no frills. The also sell pomel bags, which might look cool draped over the gas tank.