Bring a big plastic bag with you - when you need to recharge your packs, fill the bag halfway with ice and water and lay your packs flat in the bag.* They will recharge fully in 20-30 mins! You can also put them in the drink cooler.
If you find a cold stream, dip the packs in the cold water for 20 minutes - just don’t lose them in the stream. Tip: Use a net laundry bag to place the packs in the river.
*Just Ice will not work as fast, it needs to be ice water so that the packs are fully submerged in the cold temperature.