In reply to G3NYY:
Walt, if you want to play scrooge and be like me, a plastic milk bottle screw top might just be a force fit to your pole. I use one on the bottom of mine fixed with tape and while they eventually split, the replacement cost is zero and with spare bottle tops and tape taken up the summits I can effect an instant repair.
As for the top of my pole, like most people I too have lost the bung - on the way down Drygarn Fawr GW/MW-003 on 7th December 2008 if I recall correctly. Since then I have used the neck of a milk bottle taped over the outer of the pole using Gaffa tape and the screw top keeps everything in. Using red tops I can see them in low light conditions, so haven’t accidentally littered any summits.
Now if anyone knows where I can get fluorescent yellow O rings to fit the elements on an SB5 SOTAbeam, that would stop the depletion of my O ring stock.