Yessss! Migraines SUCK! And when they hit, light sensitivity gets much worse! I, luckily, don't get them often but when they come....

I'm nearsighted with astigmatism, not bad but enough to keep me wearing prescription glasses. So my sunglasses are all prescription with extra dark, polarized, anti-reflective (usually teflon or cryzal), and ultra thin to keep them lighter in weight. For non-RX, I would probably go with Maui Jim. some of the frames are a bit overly stylish for me but I do like their large lenses which wrap minimizing peripheral light. The lenses are pretty high quality too. Some of the frames are available w/RX but lens curvature can distort Rx. I'd suggest staying away from cheapies (you only have one pair of eyes and if you already suffer migraines...). Go to a high end optical store and see what they have. Really good quality non-Rx may run as high as $250-$300. Good quality Rx with all the trimmings I get usually run me closer to $500+ (depending on frames).

Back to Topic, another cheap and easy sunglasses solution is a chord around the rearview post. Measure to optimum length so as to not block lines of sight and use a waxed or heavy rubber type chord (holds its shape better - especially as ages and starts to dry out). May swing a bit but the stiffer the chording the steadier they will be.

Some of the visor clips (with spring clip) might even clip onto the over the door ceiling hand hold and keep sunglasses out of the way there - still in easy reach.