I have a OS 160 Gemini which I'm installing in a 1/4 scale cub. I removed the exhaust pipes and accidentally lost one of the copper washers that fit into the exhaust pipes inside the cylinder head. I found a washer of similar thickness and diameter but it is made of steel. I am concerned that if I use this in the exhaust it will corrode and get stuck ruining the engine. I tried the small washer from a glow plug but its a bit small. Don't know if its possible to order these things. Any ideas?

Horizon hobby is showing this in stock. Might be your only option for original parts it is what you are looking for. Good luck