I didnt use one, I just bought a tube of Permatex copper gasket maker from Advance Auto parts. pretty much all parts stores sell them.
If you have a hardon for a gasket there look on
http://www.cheapturbo.com you should find one for a T3 there (T3 is the exhaust side you'll need it for)
-Aaron
[edit] crap, they dont have a gasket there, they just have the flange. oh well, seriously I dont feel you need one, just use the permatex copper gasket maker and some lock-washers/loctite on your bolts. [/edit]