I really have no idea, but some of the guys at the ARFCOM Retro Forum collect these old flare pistols...
http://www.ar15.com/forums/forum.html?b=3&f=123
Also, FWIW, I've seen sleeves advertised to convert 40mm flare pistols/launchers to 37mm (which seem to be readily available...boaters maybe???)...
And I have also seen 12ga flares advertised...again, for signaling...It would not be too hard to make a sleeve to adapt the 12ga flares to pretty much any flare pistol...
(I'm not offering...just sayin', is all...)