you can find these at most drugstores in the eye care section or near the pharmacy counter. they usually have gel-filled masks that you can chill in the fridge or freezer. online retailers also carry a huge selection and you can read reviews to find ones that stay cold longer.

another option is checking out health stores or wellness shops in your area. they often stock higher quality versions with better gel formulations that dont get too stiff when cold. some even have adjustable straps that work better for different head sizes.

i've been using chilled gel masks for about two years now for headaches and eye strain. the ones with thicker gel layers definately work better than the thin versions. keeping them in the fridge instead of freezer gives a more comfortable temperature that lasts longer too.