Sounds fun.
I would second @Antje77 with Frio bags.
I have taken them on walking trips in distant locations where tents have no fridges and found them great for keeping insulin cool in my bag.
They can be “topped up” and reused again and again and again. My Frio bag is 15 years old and going strong.
I've used Frio wallets myself. i recommend them.
Take a look online. work out how much insulin supplies you'd take, (including a little extra.)
Then pick an appropriate bag/s size to accommodate..