As a matter of personal principle, I despise any car accessory that requires taking space in a cupholder or air vent (I like drinks and live in a desert) and for some reason my 2010 Toyota Prius doesn't have a glasses holder

Attached it to the dash with a command strip, but you could also heat up a safety pin and melt/glue it into the back to make a glasses holder that you can attach to a jacket or whatever.