It’s from an Aurora SH-035 on the tail cap end. Color doesn’t matter I just can’t find the size anywhere.
Aloha! I bought a bunch from ShiningBeam.com along with a few flashlights. Very fast shipping and excellent customer service.
http://www.shiningbeam.com/servlet/the-Parts-%26-Accessories/s/9/Categories
+1 on ShiningBeam.
If they don’t have the right size: https://www.theoringstore.com/
Looks like these parts numbers are about right:
Buna-N Material 9262K104
Viton Material 9263K286
Silicone Material 5233T18
Ah, the old US problem in distinguishing between imperial and metric The intl Outdoor rings are 25mm (nearly one inch). OP wants just over 1 cm.
Still, great news that NASA landed on Mars brilliantly this time - at least they finally worked out the difference. Mind you, the Brits & Europeans with the Beagle a few years didn’t even have the excuse of confusing imperial & metric.
Looks about 12-13mm, about half an inch. Thickness counts too, probably more than diameter as they will stretch if they are a little small.
I have a kit box or o-rings I bought at a cheapie store somewhere, maybe 20 of each in various size and thickness. was like $12 for a couple of hundred. They are all boring black, but worth looking out for something like that.
Oh, but none of them are chewed up like the one in the OP. Mine are all round and smooth. I guess you could let the dog chew them for a bit?