Made it 51 years without them , but now things afar sure look a lot better through them.
Looking for a good protective case to attach or clip on to my pack to protect my glasses .

My fishing glasses by Costa always come in a nice case, they may sell these separately. You could glue Velcro to it and sew a strip on your pack. I have seen some tactical styled cases that take the Alice type clips or have their own straps this would be fool proof almost. Most packs have an accessory strap or one for a water bottle that would be a good place for the case.

Yep I just use a Costa case as well

I use this one...

https://www.amazon.com/gp/aw/d/B0049PFB6U?psc=1&ref=ppx_pop_mob_b_asin_title

I know the military used to have a hard plastic case that clipped onto your web gear. It sat vertically and had a hinged lid. Maybe could find a surplus one.

5.11 slickstick case.

As vital as your glasses are, best keep them inside of the pack (and have a spare set, too).

Are you referring to the one that Tactical Tailor makes?

I've worn glasses my whole life, and quit wearing contacts about 5 years ago. I find many of the current hardcases too big. I've been using the semi-hard case from Lowe Alpine for many years now and haven't found anything better. In my cargo pocket, hanging from my belt or shoulder strap, in luggage or carryon, in my jacket pocket while skiing - I've never broken a pair of glasses.