I got 3 units built for myself by PCBWay at a cost of $77. I got quotes of ~$500 for 100 units from Elecrow and Makerfabs, but didn't know what to do with the other 90.
Although I really want this great little gadget to be easily available, I can't afford $10,000 for FCC certification, and therefore I have no solution.
If anybody wants more details, email espusb@gmail.com and we can chat about it on there.