Not sure if this is a Class A or the Toyota Series Class C. In later model Class A's, National used...
R V Custom Products
14000 Anson Ave
Santa Fe Springs, CA 90670
...for their 12v battery control center. Since you did say "power center" (used in C's) I doubt R V Custom Products built those.
Below is a replacement "power center" from Progressive Dynamics. You can compare the dimensions to see if it will fit. If not or not sure just contact sales Sales
Mighty Mini All-In-One System AC/DC Power Distribution Panel and Inteli-Power Converter