well, I may be wrong here... but if you dare to check pawn stores with lots of clothing, you can always stumble on BDU's. And as it seems, most of those BDU's are issue BDU's that ex-servicemen are discarding because they've been sitting around in a closet forever. I mean, i'm pretty sure the BDU's i have are all issue because they've mostly come outta those stores and have been around for me for years and years, and are all just a bit different in material that a lot of the new stuff I see guys out with.
And yea... I have a friend (old neighbor) who got me some BDU's when I was younger from the ANG years and years ago.... and I know they're issue.
So getting older issue patterns isn't really to hard to get. Its just the new stuff. I mean, not 2 years ago all I saw photos of in magazines and in the paper was of solders in 3 color. No MARPAT to be seen.