I hunted around the web and discovered bad news. First, the Pyramid company changed its name to something like Pyramid Car Audio, in Brooklyn NY.
However their web site seems not to exist.
I suggest you find a workaround to solve your problem. Perhaps fabricate a new panel and put in whatever meters you can find to do the job. There isn't even a parts list out there for your model.
Given all the above, I'd suggest that Pyramid is a name to avoid. If your unit works otherwise, be grateful, and rebuild it with available parts.
As an engineer who has designed many power supplies, I feel that these units aren't difficult to create. The hardest part is to find reasonably priced parts, so the best solution is swap meets. The Astron brand seems to have survived years of operation so maybe that's a way to go.
Good luck!