Go to your optician. They should be able to find some that fit you and if not you can usually choose a frame that you like and they'll order it for you in the correct size. The optician should also be able to adjust them for you, you could do th is yourself but its better that they break them rather than you!

Last week I actually went to get a new set of prescription sunglasses. The most comfortable I've found are the rimless titanium bendy ones. As it's rimless they can just make the glasses wider by making the lenses bigger, this does make it thicker near the edges however so it's a tradeoff. They're also not cheap, together with my high astigmatism which requires the thinnest lenses the total was around $700.