I did notice that the Polar Bear website shows pretty much all of their soft cases as sold out. .
Check out eBay. Quite a few Polar bear 24 soft coolers, new and used available.
I have used both the 12 pack backpack and 24 pack suite case as a carry-on.
Backpack easier to carry around, suite case holds more.
Plan to empty everything when you go thru TSA.