easy! get the haze book of fibs to help you do this jod!
however i dough if you can get just a gasket so you may need to make one from a cornflakes box (like i do at times) then use sillycone as a jointing compound, (any kind of sillycone will do but instent gasket is best) read the book first!!! its only two hours work even stoping for lunch,
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