I've seen a few DIY solutions that I like.
For a single wheel trailer, I think it'd be hard to beat cloning the U-hook over axle extensions of the BOB trailers.
For two wheels, a rubber hose is decent, but I think I might go with an air chuck as a quick release and a couple of 3/8" ratchet universal joints, all welded/brazed/whatever together. I've seen both used.