First rescue dummy I ever used was at the Boy Scout camp I worked at. The camp ranger had stitched it together out of some of the old canvas from tents and stuffed it with rags of the same. I think there might have been a solid chunk in the middle to add a bit of weight too.
Another rescue dummy I've played with was also home built. 15 gallon barrel for the torso, arms n legs made from anchor chain. Whole thing wrapped in furniture foam, then manhandled into coveralls bought at a garage sale. IIRC, it took another couple feet of chain in the barrel to weight it up to about 180, while still leaving a bit of room to adjust.