The Chewbacca’s were found to have used the same hair as the 75 Kirks, about 10-11 years ago. They are from the years 75 to 78. There no certainty with other Don Posts masks. But the vintage Chewbacca’s come up on ebay about twice maybe 3 times a year. I immediately got 2 of them, 10 or so years ago, they were $50 then, and I rehaired 6 masks with real Kirk hair. I have a stored stash of the hair.
There isn’t really any definitive answer though. Bill Malone said crepe wool, Rob and Cathy Tharp said it was closer to mohair, Josh lab tested real kirk fibre and it came back yak belly hair. So what is the answer? I wish it was as easily obtainable as you are making it out to be I’ve been searching for the answer for a very long time. So please share!