I would like to buy (preferably online) a concert T-Shirt from Pink
Floyd.
It is a PINK cotton cloth T-Shirt with the following silk-screened on
it:
On the front: "Oh by the way ..."
and on the back: "Which one is Pink?"
That's it.
I believe it is a concert T-Shirt from their 1987 Delicate Sound of
Thunder tour.
I DO NOT WANT someone's custom-made replica of this T-Shirt.  (I'm
sure this is simple to replicate)  I want an official, original, NEW,
authentic T-Shirt in size large.
Can anyone find one?
Thanks

Wow.  You are looking for one of the classic concert tees of all time.
 In doing research, it appears you are not the only one.

One I found was http://www.star500.com/pink.html they have a wide
variety of original Floyd concert t-shirts, though not the one you are
looking for. They say if there is a shirt you are looking for to email
them and they will find it.

Another option you may have are the through the various fan-sites and
newsgroups that are out there and see if anyone has a source.  Here
are a couple that I came across:

http://www.rogerwaters.org/main.html
http://www.pink-floyd.org
http://www.allfloyd.com/
alt.music.pink-floyd

Good luck in your search