I used to fly radio control aircraft, just about everyone made one of those to carry their planes.
Get some PVC pipe, a saw or PVC cutter, some elbows, tees and some pvc glue and primer.
I think that 1/2 inch is too weak, I like 3/4 much better.
Dream it, build it.
Put it together without glue first to check the fit for your hardware, and to make sure that it will fit in your car. If it's okay then glue it.
If you go to a bicycle shop ( or walmart) you can get a cup holder for it!