I work in a very dusty environment, and found that my torch and gas tank would often get particles inside that would screw up the piezoelectric igniter. This is the solution I designed.

This gas cap will fit a standard 1-lb propane or MAPP gas tank, of the type you get at Home Depot or Cabellas. The plug fits nicely into my Bernzomatic TS8000 blowtorch. However, I would assume that it'll fit any gas inlet, for lanterns, camp stoves or turkey boilers.

Both are threaded for 1"-20, and the threads are about 7/16" long. The tops of both items are magnetized, and will stick to a bottle, steel tabletop or any other metal for storage while the torch is being used.

Edit: I haven't gotten to it yet, but I'll upload left-hand threaded versions of both cap and plug for oxygen bottles and inlets.