I recently bought a nice little diamond dust sharpener for all of about $2.50 from Kaufmann's. I've only used it on two hooks, so i don't know how long it will last, but it works great. It's equal to, if not better than, my hvy duty Tiemco ceramic. It looks just like a thin metal nail file, but with diamond dust all over it. It weighs next to nothing, and its thinness allows you to get a good angle on the two top edges of the point. I'd be surprised if it was stainless at $2.50, but at that price ..
Kaufmann's is 800-442-4359
I got mine at their Bellevue store.