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Been using mine for years. My system:
All of my supplies are kept in a Dia-Pak Deluxe:
Medicool - Dia-Pak Deluxe - Since 1989 Dia-Pak has been the product of choice to keep insulin and related supplies organized and portable .
The insulin pens are in a Frio pouch that just so happens to fit perfectly in the Dia-Pak. The Dia-Pak then goe in an Igloo box that has a very large blue-ice block in it. It can actually get too cold, so I sometimes use some bubble wrap as a separator. I really only use the Igloo box if I think the car will be parked in the sun for an extended period.
If I need to carry the stuff with me, I just grab the Dia-Pak out of the Igloo box. Everything stays cool. Another advantage is that there is plenty of room in the Igloo box for "doggy bags".
Sounds complicated, but it's really a very simple solution.