hit or miss really. some shops don't want the hassle of having open sets of rings sitting around on the shelves, and it's easier for them to force you to buy the whole set.

but yes, 440source has "single cylinder" ring sets available from the "name brand" suppliers. I think they're stocking Total seal rings.

if no one local to you will sell you a single piston set of rings, then you can hit of 440S.