Engine or the drive? BGF is Asian and has his connects, the two components are something he's putting together I'd say. The engine is a noisy Chinese made copy of the better quality Mitsubishi or Tanaka class engines and available at Monster: 49cc/52cc Scooter Engine with Manual Pull Start
among other places.
The drive is a copy of the Staton FD that several other vendors have appropriated as well and I'd guess BGF just off-shored a version using the American made prototype but with lesser quality components.