Reddit reviews Flents Sports Band - Elastic Eyeglass Holder for Active People

this should work

Can get a band that goes on the ear pieces and around the back of your head. Should tighten, but if it doesn't just use a rubber band or a binder clip. Try to find something like this

This isn't a full solution, and probably only for work.

That's what this is for. That and titanium/flexon frames with scratch/shatter resistant lenses.