Or can I buy a replacement (unpainted even!) back plate somewhere I can drill into to attach the voodoo labs battery snap connector?? Don't wanna damage the original backplate and not a fan of battery power at all (sorry battery aficionados!)
Analogman uses several sized enclosures. What particular effect of his are you referring too? You can purchase bottom plates for some sized enclosures thru Smallbear Electronics. It's a matter of just drilling a hole, inserting a rubber gasket on the drilled hole and inserting a power cable. An easier method would be to drill a hole along the edge of the bottom plate and insert the 9V batter adapter power cable.
I believe that particular pedal is a variant of the 1590B enclosure by Hammond. The Hammond bottom plate will not fit it, but I would check Smallbear Electronics to see if they have a bottom plate for that enclosure.