Just about any lockring will work, except Lee. I do think Forster's lockrings are the best to use with it though. Darned things are pricey, too. I never thought about it, but I guess I've bought about 60 of those suckers.
You're going to LOVE your Chargemaster! The insert is essential once you've experienced the improvement it will make. You can make yourself one out of a 5.7 FN case, ya know.
God I am hating caliber threads more and more