What type of robe?
We use something similar to Dearfoams, I think they're just called scuffs? Not sure where she got them, it could even have been the Family Dollar. They're a very fine, soft terry with one wide band that goes across the top of the foot. They have rubbery soles. We just throw them in the washer and dryer and they do fine. We've got a couple of pair that need replacing after 5 years because the edges are starting to fray a little but they're still functional. Since they're only wearing them between rooms and not all around the house at night (like I do, lol), we're gotten our money's worth.
http://www.walmart.com/search/search-ng.do?search_constraint=5438&ic=48_0&search_query=slippers&Find.x=32&Find.y=13&Find=Find
Scroll down to the bottom of the page, they look like the pink and blue ones. If you can find something locally for about the same price, you'll save on S&H.