Re: Prescription sunglasses
I'm not sure they have what you want, but it might be worth ringing Optilabs (http://www.optilabs.com/). They have nothing aviation-specific on the website, but I'm sure they have conformant lenses. It will probably be cheaper than what you get at other opticians. You can also send them a frame and have it glazed. I've dealt with them, their customer support is great.
András