Vic
That has got to be as rare as rocking horse ****!!! The chances of a stock are pretty unlikely, but Ian Shirra Gibb would be your best bet, he at least is old enough to have seen one!
If you had infilling and inletting available the 300SU air rifle stock is the same externally, but that would be a pretty big job, or better to drill and pin/glue up the wrist with either a wooden dowel or I've seen them done nicely with an alloy bar.
Best of Luck
Robin
Walther KK500 Alutec expert special - Barnard .223 "wilde" in a Walther KK500 Alutec stock, mmm...tasty!! - Keppeler 6 mmBR with Walther grip and wood! I may be a Walther-phile?