Austin Homebrew Supply has a new streamlined kettle conversion kit.
Stainless Steel Kettle Conversion Kit (Economy)
Add an all stainless steel ball valve with a 1/2" barbed nipple to your kettle. To attach, a 7/8" hole needs to be drilled into the kettle. There is 3/8" NPT threading on the inside of this kit so you can attach a nipple or kettle screen.