I agree with most of the above comments.
i have been shooting a Triumph for since that came out and an Endeavor For a few years I have yet to replace an "o" ring: I do keep some spares. I bought an O ring box that has many sizes because I use them on many things tractor, lawn more,chainsaws, backhoe,and etc. one of the o rings in the of graduated sizes is the right size and there was about a dozen in the box so that's where I got mine. It must be a standard size to be in the box. I took the original off and tried one to be sure they fit and would work . You should be able to get at any good hardware store or farm store. I strongly agree with having a back up, I use my Triumph to back up my endeavor and if needed I could dig the Omega out of storage.
I do have to disagree with one thing the rem oil has Teflon in it and so I do not use it in the bore as Sabot loader taught us about the problems that can cause.
I use Montana X bore protector and am quite happy with it.