I'm about to head down the US east coast and know it will be hot (100 F in DC yesterday).

I intend to take a portable fan. I've seen this:

and even this.

Any others I should look at?

The latter looks like it employs evaporation cooling which has very limited effectiveness or simply doesn't work in high humidity...as you will almost certainly experience on the East Coast. It probably works OK as a fan though. I was in a discount department store just a few days ago and saw one which was identical the the first one you linked to... Don't remember which store it was.

I think I'm going to go for more batteries (hopefully implies longer running times):

4 AA's

On a previous trip I've had reasonable luck w/ this, though I'm hoping for better. I also tried this, but it broke quickly.

Point taken re evaporative cooling.