I think Brownell's carries it. Liquid wrench is also good. And, as a gunsmith, I can tell you that cayugad gave you some pretty good advice. This thing with heat and cold can make an amazing difference. As well as spending some time trying to soften the cause of the seizure - which is powder fouling and residue. At the end of the day I hope you don't go through all this and find out the bore is badly pitted anyway . . .