I tried a few different things. Some of them ended up fogging my glasses, others maybe were too thick to fit a helmet over.
The one I use all the time is:
https://smile.amazon.com/gp/product/B0012TZ04E/ref=oh_aui_detailpage_o09_s00?ie=UTF8&psc=1
It's very thin. I still wear a winter hat over it, then a helmet on top of that.