Need an o-ring slighty fatter than the standard C/P/G tailcap o-ring

I have a Surefire 8AX commander and I don't like how loose my KT5 turbohead screws onto the body. I experimented a little and found that 2 of the standard size orings that's used on the tailcap section of 6P and G2 lights can fit into the last groove on the 8AX's body, but if they were just a little bit fatter they would be perfect. Does anyone know where I can get the same sized o-ring just a little bit fatter?

Lighthound

Yes I know lighthound sells surefire sized o-rings, but I need one slightly fatter than the standard size they carry.

McMaster Carr

A trick that I've found useful when standard sized o-rings are just a bit too small is to use teflon tape to make them fit better. It works pretty good as long as you have the o-ring sitting in it's own slot. I remove the o-ring from it's slot and then wrap several layers of teflon tape, used for plumbing fittings, aroung the slot. I pull it tightly so it goes down into the groove. Then I put the o-ring back in. The teflon tape in the bottom pushes up the o-ring to get a better fit. You can repeat the process as needed until you get the tightness of fit you like.

Take your light with you to a local hardware store or plumbers supply shop. Most of the mom-and-pop type stores sell o-rings individually rather than a bag of 5-10 like the big box stores. Not sure if you have a True Value near you, but the one near me has loose o-rings in a compartmentalized drawer that makes it quick and easy to find the size you need.

bearing supply shops and hydraulic equipment shops stock a range of orings.

www.oringsusa.com. Shipping is $7.50 so stock up! You'll probably want the nitrile material rings which are designated by the BN prefix IIRC.

Another online retailer is http://www.theoringstore.com/

Check the "AS-568 O-ring Size Chart". I believe that the 6P tailcap o-ring is a -017 but not positive.