Same place you get the decapping pins. A RCBS stuck case remover is just a collar, drill bit, 1/4" tap and and allen wrench. Just out of curiousity did you wreck the decapping stem, the pin, the expander ball or all three? The idea is to loosen off the decapping rod and move it up in the case to make room to drill it out before you break anything. Then you slip it all out the bottom and do whatever you need to do to get the assembly out of the case. I usually just cut the base of the case with a hacksaw.
It sounds like you have a oversized chamber in the rifle, I've had a few of them. When things are normal, you should be able to size .223 with little more than the weight of your arm on the lever, and pull out just about as easy. It is possible to get a loose chamber tight die combination that will stick the occasional case even if you do everything right. If you feel anything like excess resistance going in, stop and relube the case before you stick it. There's enough crap barrels out there to try your patience, believe me.