Lands End has casual button shirts made of quick dry mostly polyester ...
http://www.landsend.com/cd/fp/prod/0...43683422114090

LLBean has an even nicer nylon/poly blend shirt ... light & airy (and available in Tall)
http://www.llbean.com/webapp/wcs/sto...feat=ssdpa6266

I think both make other similar shirts.

Personally, I have had pretty good summer luck wearing a wicking undershirt (A or T) and then a slightly loose lightweight cotton shirt (usually collared w/ buttons) over it. Seersucker would be ideal for this. The combo is surprisingly cool and breezy.

Good luck!