BGfisher

Have never used the products I'm about to mention because I leave the glasses at home, but try one of the commercial lens defoggers used by scuba divers. You might have a shop nearby.

Another one we often use for diving is a mixture of water and baby shampoo. You could try it in a squeeze bottle, but requires another container of water to rinse it off. I know it owrks well on my scuba mask.