I used a Hammond 1444-16 aluminum chassis that I ordered from Mouser.com. John Calhoun includes a template for this chassis (10"x6"x2") in his instructions.
Re: the holes, I handled eveything on the chassis with a regular drill set, except for the tube holes (got some panel punches from our shop here at work for those; worked great) and the IEC connector, which one of our shop techs cut out for me with a jigsaw.