@Michael,
A couple of years ago, I ordered a blue nylon seat cover for my Brooks B67S saddle from Randi Joe Fabrications. It has held up very well. I am very happy with it. There is a feature on the seat cover, a flap that extends up and underneath the saddle to protect the it from rain water and dirt from flying on the underside of the seat with snap fastener. I do use this, because my bicycle is full fendered on both wheels. Also, there are custom elastic holes to mount the cover around the metal rear saddle loops.
Overall, it is a finely crafted and well designed bicycle saddle cover. I would not hesitate to buy another one, if mine were to get lost or damaged.
As for the waxed seat cover that Randi Joe offers, it my need regular attention in replying a specific wax periodically to maintain its water repellantcy ?
You would have to ask Randi Jo.
Kim Hetzel.