Yeah, I’m looking for something like that. Would be nice if I could buy a finished product. I’m just wondering how to attach it, since the dolly’s drawbar is not straight but fork-shaped.
I found this one myself,
https://www.merseatrailers.com/store/Trolley-Coupling-Bracket-for-Launch-trolley-coupling-p156595141
It looks handy, but unfortunately it doesn’t seem to fit directly and requires a bit of modification to the trolley anyway.
However, it would be good as a model if I could make it myself. Metalwork is quite foreign to me, and I don’t have welding equipment or the skills. I have better tools and knowledge for woodworks. But maybe it would be sturdy enough with just bolted joints. Buying from a metalsmith would also work as a made-to-measure order, if I just could find a small workshop that would do individual work.