You can buy them at any West Marine or Restaurant supply shop, a lot of tackle stores carry them as well.
A good knife should hold an edge well and just need a few swipes on a steel before you use it.
I've found the electric Chef's Choice models to be pretty good for all my kitchen knifes. They make a smaller manual model you can usually get at Homegoods for prety cheap.
Just get somthing easy to use so you'll actually do it
-spence