I got a Cabelas magazine this week and saw one in it and they are also online at Cabelas....Don't know if they are anywhere else or not though.
I tried to paste the link but didn't work...you can to Cabelas website to the boating section and they are listed in the accessories. I imagine that if I had on I'd put it on a RAM so I could take it off when I'm sleeping at hotels on those weekend trips...