Try this new shop in bangkok opened by a thaiairways pilot.Transair is a ripoff for the same exact price in pounds you get it in dollars at sportys.
It's located on 2nd floor of Amarin Plaza 496-505 Ploenchit Road close to the Chit Lom BTS station. try
www.aeroshopbkk.com
Or call +66 (0) 2256 9786
Cheers.