Hi James,
I have an original (non-substantial) plastic one that I've reinforced with wood, and then tucked off in a corner.
I don't know of anyone that has done one specific to our cars, but I've looked at several DIY stands that folks have made for their Porsche, Mercedes, etc. tops that look pretty straightforward. Black pipe and foam swim noodles or pipe insulation, pvc, and the like. Half a wood pallet with nice caster wheels (larger than you think you need) might be a good, solid foundation I was thinking.
I'm thinking about making one up...just to do it...after all the other projects...are...done...
Good luck!
Steve