White elephant

So, I discovered this afternoon that the "white elephant" vax steam cleaner that Mrs P bought several years ago, and has at least a quarter of an inch of attic dust on, will run my small small engine. Isn't steam good at pointing out leaks!. It never leaked whenI ran it on compressed air. I need to make a gasket for the cylinder head, and seal the thread on the steam fitting. What sould I use to seal a small thread and make a thin gasket?

mmmmmm humble pie for tea tonight.........

I've used a cappuccino machine before now (I even have a salvaged boiler from one waiting for a case). I've also looked at an Earlex wallpaper stripper - they have a kettle element and a radiator cap on them set for about 4psi, so plenty of pressure to raun an engine, even if not very powerful, despite being plastic and square.

Neil