If you search the forums a bit, you will find all kinds of homemade repair or shop stands for trikes, generally made of PVC pipe. I have a better one, one which gets the trike up at a nice height for working on stuff. It is also very stable, and will hold the trike horizontal, vertical, or any angle in between. It is a Park PCS-9, and sells for about $130 at Park Tools. However, there is one critical modification that has to be made to make it strong enough to hold trikes, and that is to make a metal bushing to replace the plastic one that it comes with. The legs fold up to make it easy to store or transport.
I was lucky enough to get one by Bruce, but I don’t know if has any more for this unit. The bushing to replace looks like this: