I did a very quick Google Search and found these, there were several suppliers with various prices. I've seen a similar set in a Toy Hauler/Enclosed Trailer. They seemed to work pretty well. Another thought is to see if a Toy Hauler/Enclosed Trailer Dealer has a set for sale.
If I keep my Argosy, I'll probably buy a set....there cheaper than I was priced for a used set from another Argosy.
*1975 Argosy-Airstream 24
*1995 Palamino Mustang Popup Camper
*1996 Buick RM Wagon 5.7L V8, AT/OD, tow pkge, coil over shocks, hitch, brake box, cooler.
*Good Sam Club Life Member