Cylinder o-rings

Hey guys, I noticed that a few of you had removed your cylinder liners from the block. Did anyone happen to find a source of the rings? I have three blocks with various quality liners. It would be good to put all of the good liners in 2 of the blocks rather than have to attempt the expensive rebore process.
I did remove two of my worst liners from one block. Whilst both of the upper brings look like normal rubber, one of the lower ones was orange but the other was black. I know there was some contention over piton (?) brings but the black one I found suggests just normal brings.
I would appreciate any suggestions on where to get them and what to do