Another water bottle freezer here… Even in the work plane every day / night I carry my lunch in a small six-pack cooler that I cool with two frozen 20oz water bottles. By the end of a longer night or day, if I've consumed the sammich and pepsi or whatever they were cooling those two are thawed enough to pull out and set next to me for even more cool water as needed.
And another pre-cooler as well… For a couple decades we used a Centennial range back pack hunt as our back up for when we couldn't draw an elk tag in AZ or CO. There is a bar in Lima Montana that boasts the best chef in town…mostly because it is one of those places where you order your steak, it comes out on a plate raw, with your potato, and then you scooch yourself over to the pit to cook it as you see fit

. This was always a mandatory stop for us as we could always pick up a brick hard frozen porterhouse to slide into the packs. Most of the time it'd go 3 days before it'd be thawed enough to mess with, and by then we'd be ready for a meal with some 'substance'… I still routinely use this same practice in an airplane. It's amazing how much less ice you need when everything starts out frozen, and just how long you can go packed this way…
Ditto on dry ice, I can't even guess how many pounds of caribou, fish, and clams have made it home to AZ from 'out west' in AK with dry ice in my coolers…
Take care, Rob