So after some research, I found that the cheapest possible way to create a gel thermal mass for both holding heat and slowly transferring it to an IV bag, ( slower than just liquid water so it does not cool too quickly) There is a material was originally developed to control absorption and release of water in soil. Not too dry and not too wet. https://en.wikipedia.org/wiki/Polyacrylamide

Gel Polymerization is the fastest way to create a Gel from distilled water, why distilled? We we don't want anything funky growing in it after the water has been added to the gel material. This material is very cheap and I believe is the easiest and fastest way to create a thermal mass gel for stability and general heat retention.

Please Like and Follow as this will dramatically effect my ability to make this project better and more practical as an actual field ready product. Thank You!

Here is Gel material plus water filling the spaces between the water beads. During testing we can use the level of water added to fully saturated water beads to adjust the thermal transfer rate and heat retention.

This is the same water polymer with no water added to fully saturated beads. Water beads without the water filling the space significantly reduces the rate at which heat is lost from the gel mass in the sealed box.

Please Like and Follow as this will dramatically effect my ability to make this project better and more practical as an actual field ready product. Thank You!