Mersea trailers are still in business:
http://freespace.virgin.net/trailer.sales/
I don’t like their standard road base. Get some decent
wheels and tires if you plan to use it on real roads.
The standard wheels and tires are too low unless you
remove the wheels of the trolley every time, something
that is easily forgotten. Several fellow Wayfarer sailors
have experienced punctured tires with the standard tires
in less then a 1000 miles. Make sure to get car tires or
equivalent quality.
In short: bigger wheels to get the trolley wheels higher
up and better tires that don’t puncture easily and are
capable of at least 60 mph for prolongued periods.
(Bigger wheels also means les rpm on the bearings).
I got a decent solution through Porters but I would need
to check (it’s at the club) what brand it is.