I had the same issue after roaming the internet no one seems to sell the part! So I got a metal drill bit, I took the rear bolt off the side where the motor stopper is on and drilled a hole right through the frame and into the Motor stopper I then inserted a small nail with a flat head into the hole and tightened the bolt onto the head of the nail to keep it in place! I’ve been using the bike again for the last week with no issues! So fingers crossed