Hi Gary
Here is where I got one last year,
http://www.obschevy.com/ not list in their online catalog but they don't always list stuff they have only a few of.
So I would give them a call 1-800-248-8785 or 1-229-686-5812 tell them what you need.
This is the place I got the NOS 4 speed for my truck last summer. I need a real housing because wanted to put my original trans back together as a complete spare.
Cheers Phil