C8 O ring set needed

In need an O ring for my C8. Its a standard size head. It is the one that sets inside the bezel in the lip. The lens sets up against it. Anyone know where to get this O ring or I would be willing to buy a set if needed.

Thanks!

http://www.fasttech.com/products/1607/10001027/1208508-water-tight-o-ring-seal-42mm-2-pack
or
http://www.fasttech.com/products/1607/10001027/1328300-water-tight-o-ring-seals-5-pack

there are also sets of 10 pcs at fasttech site

THANKS !!