I have found purchasing glasses can be hit or miss weather I buy $600 glasses or less that twenty dollar glasses. I may miss a bit more with cheap glasses, but I can take a lot more shots.

I've used zennioptical.com and it has worked really well. I've run into frames that do not fit, but they were cheap mistakes and once I found something I liked, I just reorder every few years.

Paying attention to the frame measurements is pretty important if you buy online.