Reading glasses are just like your camera. The best pair of reading glasses is the ones you have with you. The ThinOPTICS Keychain Reading Glasses ($25) are so tiny and strong that you will always have them handy. They are made of an ultra-flexible titanium alloy and have a nitinol bridge (10x more elastic that spring steel).
These keychain reading glasses are available in low range (+1.50), mid range (+2.0), and high range (+2.50). The glasses are designed to fit anyone and are guaranteed to never break. For $25 it is worth a shot.