I would imagine Classic Billiards has the missing parts.Looks like it's missing the foot apron (3 pieces, which includes the ball storage tray), and at least one corner shield. The foot apron could be easily replaced with a single piece of poplar. The corner shields are typically sheet steel. Easy enough to fabricate, if you have a metal fab shop nearby.
$800 is a bit steep for this one. But, as you said, you should be able to get it cheaper.. I might suggest $500 or less.