Prescription lenses for sunglasses - any advice?

[rgG]

I would check with Costco if you really want to use the frames you have.
To get sub $200 sunglasses, I think Zenni is your best option, but you would have to get new frames, as they won’t just do lenses.
Zenni does have polarized lenses, I have some. They do have high index lightweight lenses, but I don’t think they have trivex, specifically.
I would see if Zenni has any frames similar to what you have and like, as I am pretty sure a new pair with lenses will be much less than just the lenses elsewhere.