That machine is one I returned back to a treadle. Before I got it someone had motorized it. The motor was gone, the treadle foot plate, pitman arm, dress guard, big wheel and screws were missing. I got most of that from the US via forum members on another forum. The pitman arm, derailer and it's spring cam from Australia. They are made in China.
The pitman arm was wonderful. But the derailer was horrid. I had to finish machining it so it would work.
I had to go there because at the time I could not find all the treadle parts here in the US.
You can sometimes find them on eBay, but don't hold your breath.
Joe