Cough drops, spare glasses, zip-lock bags (usually for spare food), safety pins, Q-tips, adapters, Tums, Imodium, Pepto-Bismol, band-aids, antihistamine, nail-clippers. Pens, lots of pens - they tend to walk away.

Other than prescription glasses, you can of course buy the above list as needed. But ... you get to access the value of having right on hand your preferred whatever vs going cross-eyed in a foreign store trying to piece out the language. Or having to buy a pack of 18 when you just want one.