Bill, I've seen some of the guys from the southern fishing shows wearing those head wraps and they look like they'd do a good job.
Chris, the shirts I have with the arm pit and back vents, along with the high collar came from Mountain Equipment Co-Op in Toronto. Excellent shirts that I've probably had for at least 10 years.
I also wear another shirt made by Columbia that is very light and comfortable and has a full width vent in the back. I got that one from CTC for something like $50.