Costume shops might have fox tails. And ears are relatively easy to make yourself. I'm pretty sure you could find them online, in cosplay stores. If you have something like that in your town, then you could have a look there, although I live in a pretty big city - we have our own anime con and all - and even here, I can only find cat ears and the like. So, depends.
Alternatively, you could make a template out of cardboard, and glue on some fabric. Or you could make it out of wire and then cover it with fabric. You could probably find something furry if you go to a craft store. Then you just attach it to a headband.