iSTAT Transport Bags

I'm looking for suggestions on an insulated transport bag for our iSTAT analyzers and their cartridges. We currently keep the instruments and a few cartridges in a padded/insulated bag for ease of transport and to help keep temps consistent while moving from indoors to ambulance etc. (we use them on neonatal transports) I've recently noticed that the minimum temp in the bags has fallen below room temp acceptable ranges for the cartridges during our colder months and feel that changing our transport bag might be the easiest way to solve this problem!

Thanks!