Something like this:
https://www.toolsofthetrade.net/truc...ble-woodshop_o
From what I can see for a "workshop trailer" the least expensive route would be to buy a cargo trailer and build something in. Or go for broke and get one of these:
Mobile Workshops | Workshop Trailers | Advantage Trailers
As with all trailers; you still have to watch the weight.
Cargo trailer:
https://www.ronstoyshop.com/shop/6-x...cargo-trailer/
Here you go, how to make one:
https://www.instructables.com/id/Por...iler-Workshop/
Edit: May have to go a little bigger than that 6 x 14 one--for some reason I didn't think you wanted to put a car in.
Would have to be a small lightweight car.