Any good pipe repair person can replace a stem at moderate cost. This is your chance to upgrade the appearance of the pipe, so consider what might do that. I was given a Thompson Cigar house pipe freehand, stamped West Germany. It had a plain black Vulcanite P-lip stem that oxidized very quickly, so I had Norwood pipe repair replace it with an acrylic tortoise shell bent fishtail stem. It made the pipe look about 30 years younger and eliminated the oxidation problem, and was less than thirty bucks if I recall.