Here's a useful link someone posted at Survival Podcast Forum: http://www.glassesunlimited.com/
There's no reason you can't afford to have a pair or two of extra glasses in your kit. The repair kit below is from Walgreen's Drugstore and most other drugstores sell the same set up. They cost 1-2 dollars and fit nicely in any BOB or EDC kit.
Dexter Russell fleshing knife
1 hour ago