how much do I need to pay for sunglasses with UV protection?

[online glasses]

looking for UV protection, the higher price just means you are getting a hipper style or more expensive metal frames. Cheaper plastic frames actually last longer. I really love to wear those tint lenses at many circumstances, as they look fashionable and can be used in sunlight and in the dark also, but the problem is that I also have vision problem with my reading, so, I always need to prepare a separate pair of sunglasses so as to read in the sun, and I use wire-rimmed half glasses for vision correction, I just want to know where can I get those bifocal sunglasses lenses, and how much do I need to pay?