got some made in the 80s rayban wayfarers second hand for fifty bucks a few years ago in the classic blues brothers tortoise style. they are more sturdy than the new ones, a bit bigger and the glasses have a harsher angle that makes it seem as if you look down on people. back then they didn't do the rayban logo on the side, you had to check serial numbers and the lenses for the rb etching.
this thing holds up so well. i just carry it around in my pockets. the lenses are still as good as new and i have yet to manage to make a permament scratch, which is surprising considered how often they fell to the floor and stuff. they are a little bit too big for my head tho, so i need to wear some kind of headwear or headband to fixate them properly. as far as i've heard that was already the smallest size they used to make at the time.
as a backup or rather last resort i have a pair of uniqlo clubmaster style glasses.
cheap sunglasses suck and make your eyes hurt, because they don't actually block or filter light. get good ones and take care of them.