Find this project on the PCBWAY project page by searching for "VIC 20 4x 16k pcbway". You can find many different ROM files on the internet by searching "Commodore VIC-20 ROMS".
Commodore VIC 20 8 x 8k Multi Game Cartridge PCB
Commodore VIC 20 Bundle Inc 16k Expansion & Huge Lot Of Games/software
Commodore VIC-20 ROM RAM Expansion Cartridge
Commodore VIC 20 32k RAM Expansion Cartridge PCB
Commodore VIC 20 Diagnostic Test Cartridge and Harness VIC-20 VC-20
Commodore VIC 20 Avenger Boxed Game Vic-20 Cartridge
