Wrap them in foldable ice packs in my handlebar bag
Ice packs are unnecessary. I've taken them on backpacking trips and had them the next day, after hiking in 90+ degree heat.
(of course if you get GI issues from following my advice, I am not liable, I am not a doctor, nor do I play one on TV)
My photoblog http://dragons-fly-peacefully.blogspot.com/
Bacchetta Giro (recumbent commuter)
Bacchetta Corsa (recumbent "fast" bike)
Greespeed X3 (recumbent "just for fun" trike)
Strada Velomobile
I will never buy another bike!