Looking for a book: belt, fox, woman, boy, transform, gun.?

My boyfriend is looking for a book he read as a child. It was likely published before 1992. It is about a woman who has a belt that transforms her into a fox when she wears it. A boy gets ahold of this belt and is stuck in fox form, going for the chicken coop until a male is able to get it off of him.

It may be a story in a book, or it may be the whole book. He's pretty sure he read it before he was 10, so he would have gotten it at his school's library. He *thinks* these details are correct.

I've been looking, and the closest I can get is a German story of a schoolteacher who puts on a belt and when it's shot off of him the place is named "Fox Hill". This is not the story.

Sounds like some author was on Acid man....