Here's a quick side project, built entirely out of scrap wood from the workshop, and a set of castoring wheels picked up on sale from Princess Auto.
I started by searching online for a design, and I came across one on the Glen-L website. I modified the design slightly to make it as small as possible, but also keep the maximum strength.
Here's the Glen-L design...
I've added an extra triangular plywood brace to the front of the main upright for additional strength.
I had some extra 3/4" quarter round left over from the tugboat chine. This was added to the top and bottom of the main supports for extra joint strength.
After getting the motor on the stand I realized I would feel better with an additional brace on the front main upright. I ran a piece of 2x2 up each front side.