Personally I carry all my diabetes junk in a bathroom bag. I’ll no doubt be hunted down and shot for admitting this, but I rarely keep insulin chilled whilst travelling. When I went to the Costa Rican rainforest which was hotter than hell, I wet a flannel and wrapped my insulin in that, inside a sandwich bag, and then re-wet the flannel every day. That seemed to work.
I’ve heard lots of people talk about Frio’s – which are a more sophisticated version of the wet towel approach – http://friouk.com/buy/