WWW
I suggest that you contact WARR - World Airline Road Race office
they meet each year and have 5/10km races....that night there is a big party and T-shirt swop where all the various airline employees trade T-shirts.
I can't remember the address from my UAL days but i think it is in Georgia USA or your WARR office in BA or your own airline should know. The next WARR is on in Oct
regards
DOH!!! just realised you meant work shirts!!!!!
ah well for play t-shirts you can contact the above if you are interested