I searched extensively for kitsune-mask figures and could not find any. (excepting the Ninja All Stars ones which I have and love, but they do not mix well with non-chibis. And Ninja Division company is now kaput.)
With a bit of carving and green putty, it would be a relatively simple project to convert ninjas.
The figure I chose to work with was a Witch with a demon mask from a Test of Honour character set. I carved the Oni mask to more of a fox shape, and then used bits of green putty to extand the snout and add ears. For this type of work, I use the tiny XActo #212 blade.
Hmm, ninja conversions... now I might have to do some of those too!