I have a 12" domed false bottom just like that williams one and a bulkhead kit like this one http://www.bargainfittings.com/index.php?route=product/product&path=47&product_id=85
with a brass 1/2 ball valve and a SS 3/8 barb for $45+shipping
I'll even include some 3/8 silicone hose for the connection
I'm upgrading from a cooler to a keggle mashtun, so I'm trading out my fittings for a Jaybird bottom
I can also throw in a second 3/8 SS barb for the valve if you need it for another $3