Kotobukiya sells a series of several styles of eyeglasses for figs. Each set comes flat-packed and cut out of a sheet of very thin metal, ready to be removed with wire snips and bent into shape. Hobby Search appears to have all styles in stock.
I swear Volks made some for Dollfies [27cm ones], but I can’t find a link. EDIT: Andrea, who is God, says that these no longer exist.
Forever Virginia sells sunglasses and eyeglasses at about 5 pairs per sheet of transparency plastic. You cut these out and then hook them around your figs’ ears.
Toymania has a tutorial on creating your own 1:6 glasses using wire, a paintbrush and wire snips.