A cheap approach you might experiment with -- wool or other insulating sock(s) next to skin, then plastic bread bag (or other strong plastic bag; bread bags seem to work pretty well) over those socks, then another layer of socks over the bread bags. Then shoes.

It can help to have roomy shoes for this sort of thing. The extra insulation possible will keep your feet warmer. Just going up a size (or more, depending on thickness of socks) works for some of us.