What is the best heat protectant?

I have baby fine caucasian hair so I can't use anything heavy. I currently use Paul Mitchell's Heat Seal and I'm wondering if anybody knows of a better professional heat protectant, none of that crap they sell at the grocery store. Also, my hair frizzes like crazy when it gets humid. I use Rusk Str8 and it works ok. Price is not an issue, I'm willing to pay big bucks just to get my hair to behave.