Power Supply Cable Adapter for Commodore 64 & 64C – Retro Game Supply
RetroPower PSU - C64 Power Supply, C128 Power Supply, Commodore Plus/4 Power Supply, Amiga Power Supply, ZX Spectrum Power Supply, Atari Power Supply, Sinclair QL Power Supply, TI-99/4A Power Supply, ColecoVision Power
Tynemouth Software: Commodore plus/4 7 pin power conversion
C64 to Plus 4 PSU Adapter - Commodore 64 to Plus 4 +4 Power Supply Adapter Cable | eBay