Harbor Freight sells a tow dolly, which has a 2" ball (I think) which sounds like what you are describing. It's on sale now if I recall, but it only has a 600 pound capacity. I imagine it would be great for a smaller TT or popup, but I don't think physically I could move around a bigger TT with something like this.
Jeff, Laurie, + kids
Three time former Sunline owner
2011 Big Horn 3670RL Fifth Wheel
2012 Chevrolet Silverado 3500HD D/A DRW, Classy Chassis Conversion, aka "Garage Queen II"
Hensley Trailersaver BD3 Air Hitch