Just throwing this out there since I won't be there this year...
I have the contact info for the TShirt Shop. If you contact them and send them the design in advance they can whip them up and then everyone that wants one can just buy them their. Also with advance design the tshirts are cheaper by a few bucks.

Here is their contact
The T-Shirt Shop
38 N Main St
Moab, Utah 84532
(435) 259 5271
(888) 883 5271
www.moabtshirts.com