I've had very few problems with vendors refusing to sell products or services to me because it's aviation-related, and therefore a liability risk. However, whenever I'm uncertain whether such a policy might be in effect, I just tell them "It's for an off-road vehicle." Which adheres to both the spirit and the letter of the truth. A machine for which the primary purpose is to carry persons or cargo is a vehicle. And if it's specifically designed to be operated away from public roads and highways, that makes it an off-road vehicle.
--Bob K.
--Bob K.