Since your rim is not standard it is not clear any maker would have experience. I think people in the aircraft business are used to new and innovative projects.

If there is a good technical/engineering school near you drop buy and ask them. BTW, my guess is that most manufacturers get allot of people, some whom are nuts, who want custom stuff done until they hear the price.

contact people who have built monocycles, or Mr. Didi Senft