I headed to Cabelas tomorrow to pick up a Caldwell that has the picatinny rail adapter.
ive used one of those for years now. i have an adapter on almost every one of my uppers.
there are several knockoffs avaiable on amazon too... my cousin has one of them and likes it. one of the models has rail mounts they claim are caldwell compatible i have one to install and just havent tested it yet.
for most hunting.. i usually dont use a catcher though. that one or two pieces of brass i'm willing to sacrifice to the hunting gods if need be.