Fair Warning: I am not a medical professional. I am not recommending treatment of any kind to anyone. I do not take responsibility for anything that might happen to you, your family, your pets, or your possessions.
My kids are athletic. They occasionally need to ice this or that. After trying to work with frozen peas and other homemade remedies, or commercial packs, I've found something that works great for us.
We use equal parts water and rubbing alcohol in good strong zipper seal freezer bags. I put one cup of each into a gallon bag, sealed up good and tight. Then into another gallon bag, sealed up good and tight. I slip this into a simple open ended bag made from a towel, for when the super cold is too cold against the skin.
The alcohol keeps the water from freezing solid and you end up with a stiff slushy concoction that molds to your injured body part.
As I said, it works great for us. Some people are concerned about the toxicity of the alcohol (hence the warning at the top), but my kids are not so little anymore and I don't have this worry. Plus, I've tried all the non-toxic or low-toxic stuff I could find and nothing works as well for us.