My buddy and I "constructed" a cardboard bezel for his Atari Millipede upright last year, and it was a *lot* of work. Even using a template as a guide, it's more difficult than it seems. Typically these bezels curve in more than one plane simultaneously, and getting the thing to look and fit right was a challenge.

Hence, my search for a Tempest bezel.
It does appear that Atari made at least three sizes bezels for their upright games (specifically, the ones didn't have artwork on them, e.g. Asteroids), because the bezels for Centipede, Millipede and Tempest are all different sizes. Tempest appears to use the smallest bezel of the lot.
Thanks,
galaga69