there's a one-wheel heilite pop up on ebay located in suburban detroit.
very nice shape, pretty rare, and the bid is only $200
i have no part in the sale, just passing it on.
do a search of heilite camper, bidding ends this evening.
Interesting! I had never seen a single wheeled trailer before, so thank you for the education. I am not sure I would want to actually own one, but it was an interesting experiment in engineering, to be sure. I think the proprietary hitch arrangement would discourage most people from actually using one.