make your own, buy a .040 piece of copper. cut a old cylinder off a 28 ci briggs, drill through the head bolts and sandwitch the copper between the jug and a piece of plywood and again drill through the head bolt holes, bolt it down, then find a hole saw that fits tight onto the jug, drill from underneath until you are through the copper, file to fit if the saw wasn't quite big enough, don't forget to anneal the new gasket, I'd put a couple of coats of spray copper head gasket spray on it , torque it a couple of times after it heat soaks, have fun