Here is how I made an external pouch for my Peltier cooler.
Step 1: Cleaning the Surfaces.
Using Rubbing alcohol I cleaned the surfaces of the old zipper pouch and the cooler.
Step 2: Sticking the Pouch.
Using evostik applied onto the cleaned surfaces and waited for it to be dry to touch. Next I positioned the pouch and firmly pressed it onto the cooler.
Step 3: Making Use of the Pouch!
7 hours later the pouch is properly adhered to the cooler and I put my Handy 12volt power supply into it. As an afterthought I chucked in the 12volt plug as well for a neat package!