About 6 years ago I finally got so fed up with constantly changing glasses that I started getting transitions lenses.
Another problem I had was that my RX sunglasses were always too dark. The transitions darken and lighten perfectly. Yes, they are pricey, especially since they are also progressives, but they are worth the money to me.
I'm not exactly a fashionista, but I have a blue pair and a purple pair with the same RX. My silver backup pair is currently 1 RX behind.
I wear/carry a smallish crossbody purse. I don't think I will ever be mistaken for a local, but IMHO walking around with a backpack or without some kind of a purse or tote or shopping bag indicates that a woman is definitely not local. Local women will not be wearing a backpack, but they will be carrying something.
A few years back I got some mesh shopping bags from Reuseit. They weigh nothing and smush into a small pocket built into the bag. My husband's comment was that people could see what was in the bag. Mine was, that's the point. What they'll see is groceries.
Although it wouldn't be totally hands-free, you could do something like that in combination with a very small soft fabric purse or glasses case on a cord that goes around your neck, preferably crossbody. Most of the ones I've seen were in world folk arts and crafts kinds of stores like Unicef.
Of course, you will have your valuables in your moneybelt, right?