Aerborn Factory shop, ask for a seconds one though, much cheaper thats where i got mine from im sure they will do mail order as they have offered to send stuff for me before. Id go a size smaller my 6ft3 comes up more like a 6ft6, mine was £35 so a bargain and ive looked it over and cant see why it was a second.
eBay is the cheapest place to get Thermatex ones. esp if you are prepared to get one (a) in nice colour but maybe not your ideal colour) (b) one which only has a chest strap and get belly straps put on later.
I saved about half that way and it meant I got the real thing not an imitation.
BTW Ive found the larger squared Thermatex (old style) more absorbant than the new style with the very small squares. (Old style is about 2 inch squares in its quilting, new style about 1 inch).