ClipGuard

Folks like me who wear prescription eyeglasses don't have the luxury of buying any old pair of sunglasses. Instead, we use clip-on sunglasses, which in the best case are manufactured specifically for our eyeglasses. For example, see the accompanying links for some Nautica clip-ons similar to the ones I wear.

Clip-ons in this class range from $80-200. Fancier clip-ons feature polarized lenses and magnetic attachment points. Despite their high cost and model specific nature, clip-ons typically come with a cheap flexible vinyl case. If you carry your clip-ons in your pocket (as I do), the clip-ons are subject to lots of stress, and typically break after a year or so of abuse.

30-cent bananas have custom plastic cases (see link). So why not $100 clip-on eyeglasses? Someone should manufacture a low-profile hard-plastic case, approximately the right size for clip-ons, with a little internal foam to keep them immobile and safe from scratches.