You can make great "slush packs" out of two ziplock bags, water and isopropyl
alcohol.  Put three cups water and 1 cup isopropyl alcohol in a
sandwich-sized ziplock bag.  Zip it shut.  Place that zipped bag inside the
second zip lock bag and zip it shut also.  Toss 'em in the freezer overnight.
 They work great ( I use a thin terry towel to avoid placing the icepack
directly on skin when first using it out of the freezer); mould to affected
area pretty nicely, and stay cold much, much longer than the commercial
freeze pack I was using before.  Got this idea from an OT.