I believe the "scroll" Ampeg bass was of collector's value due to real hand-made DETAILS such as the tail piece.
Obviously you have two choices; to continue to look for a "parts" Ampeg (beat-up sold for parts, etc) or consider making a unit yourself. Since you are looking for a single unit, the machining might be less of a hassle than you think. Then you find a way to chrome it locally; that's simple enough.
IF you're talking about the "block" unit you could actually do that with mild steel and cobalt drill bits & a few files.
Finding a "parts" unit sale will (most likely) cost you some money because it's doubtful that the owner would want to sell off individual parts when the chances of having multiple customers is slim.
If it were my Bass; I'd make one and chrome it; especially if you have the old unit as a templet. IF you DON'T have the original there are places to find photos:
AEB1
But no specs....
