I used ice bottles, in Arizona. Fill a water bottle that won't be destroyed by the freezer partway full, pull out at bedtime, fill the rest of the way with cold water. (If the water is softened with salt, you may need to rinse off the top layer before filling or it'll be horribly brackish.) Wrap in towel. (I suppose I could have also sewn together a towel bag.) Take to bed, wrap self around.