O ring size and posible supliers please

[mobile chicane]

Righto the gas filler nozzle on my glock came with no seal O ring so I fitted one from a cheap disposable lighter but this wasnt good enough ( cheap nasty and not a propper O ring ) does anyonr know the size of O ring required and where I could get some, I dont mind buying a few hundred but not 1000's.

ta

 

[Panoptes]

Got any 16AWG silicon wire for AEGs? Pull a small bit off the wire, get a scalpel or sharp blade and cut a mm or so off. Instant washer for filler valve.