It's an industrial supplier. McMaster-Carr is their name. www.mcmaster.com Item no. 8555K36. It is not cheap though. $20 for a 12" X 12" square. I've never broke one though, even on a radio loss on my SPA3D where I went into the frozen ground at about 70 MPH, then did the most awesome 12 foot high cartwheel I ever saw. The wing on my SPA3D tore right down the middle about 8 inches, but the motor mount was fine.