Hi Jon,

I know this is the "obvious" counter-question, but do you not have a shop nearby that can lace up one for you (or service the one you are going to get for that matter)?

Otherwise, you might check with Utah Trikes. While I was looking at kits for my wife's bike I think I can recall seeing them "stock" a dyno hub wheel in 20" but not sure of the specs. I could be hallucinating as well...