We used a thick piece of scrap plastic, about the size of your palm. Round the corners, punch a hole in one corner, thread a thick rubber band loop through it and the other end of the rubber band goes around the seat belt cable. Then tuck the flat piece of plastic behind the vinyl that lays up against the inward side of the seat cushion. Worked for us. But in the end, we bought an aftermarket storage console that fits between the front seats. Gave us lots of storage and it pushed the seatbelt ends right up against the seat cushions where they should be to begin with. That would be my recommend. We didn't attach it to anything. So when we get to the campsite, we just slide it back and behind one of the seats. Great place to put all the junk from your cargo-pocket unload at the end of the day.
Good luck