Hello,
A few years ago (2004 or 2005) I owned a Buster combo. I had a separate head cabinet fabricated by a company called J Design Cabinets (
J Design Guitar Cabinets )
Jeff ("J") did a great job. He may still have the measurements/templates and be ready to make another.
Jeff used actual Mesa/Boogie black tolex to cover the hardwood. Built straight and solid, just as if Mesa/Boogie had made it. Looked great, too.
I gave up on all-tube bass amps in 2009 and sold the Buster head in the J Design cabinet to a very pleased buyer. Kept the 2x10 speaker cabinet.
J Design is in northern California, but this may work for you.
Best of luck,
--Joe in San Diego, CA