I am not sure they carry them any more (BQM). I bought one last year and it was from the website and I notice they are not there now. Actually, I have used poncho liners for decades and I have noticed very little improvement with the Thinsulate. Not worth the extra expense!
I will say, be careful when buying a poncho liner, some of the aftermarket, non-military ones are smaller. Also the Wiggy's one I bought weighs a ton, it is made of some very heavy fabric, not the light ripstop nylon. It was cheap though! We use it for a blanket on the kid's bed and would never carry it to the field.
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No, I am not Bear Grylls, but I stayed at a Holiday Inn Express last night and Bear was there too!