I have wet okole covers - not sure what you guys have (truck details in your signature help). Welcome to the forum, both of you guys!
The only thing I can suggest would be based on a wet okole neoprene cover- which is stretchy. I'd cut a small hole, and stretch it around the back of the knob, so the knob is exposed. I did this with the seatback recliner handle and it looks/fits perfect. Not sure if that will work for you guys or not. I have left mine covered, it seems to deflate minutes after cranking it up anyway.