Toxidomask

I already have a used STR cam seal, I took them out so many times that the O-rings dont seal right anymore. I did search but found nothing about it, so Im asking the members of HT if any of you ever replaced to two O rings from the STR plug. I did take the old ones off, they were dry and broke off. My question is where do I find or buy the right size O rings for this. Thanx for your time.