Here is a recipe for a reusable ice pack that is wonderful. Works like the ones that you can buy for $15 but a lot less to make.
The water doesn't freeze hard due to the alcohol, but it is sort of mushy and forms to the area that needs to be treated.
Reusable Ice Pack
1 part 70% rubbing alcohol
2 parts water
2 gallon size ZipLock freezer bags
Take one bottle of 70% rubbing alcohol and pour the entire bottle into a zip-lock bag. Zip the bag closed and place in at least one more ZipLock bag to prevent leakage. Label the bag "Not Edible."
Place flat in the freezer. It will take about 8 hours initially to get it cold.
Take it out when you need it. Wrap a towel around it before using. Do not leave the ice on for more than 15 minutes. Do not fall asleep while the ice is on you.
When finished, wipe off the ice pack and refreeze.
Use the double zip ...zip lock freezer bags...
Other things I've used include pouring corn syrup in a baggie, then double bagging it and freezing it. It conforms to whatever it's on because it doesn't freeze hard.
I also like to keep a bag of cheap frozen peas or corn on hand, and it works very well for icing sore body parts.
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Another good idea:
The school nurses in our town put damp sponges in small ziplock baggies, and freeze. The kids 'borrow' them, then return them when they're done. They work great and are good for infinite uses. Probably a little less messy when dealing with kids (what kid wouldn't eventually decide to open the bag--LOL!).