Here is a basic schematic of my Commodore 64 cartridge circuit which supports a 128 KB ROM chip (specifically, a 27C010 EPROM).
It essentially conforms to the Magic Desk 1 cartridge circuit design, where writing to $de00 will bank out a corresponding page of memory from the cartridge ROM to the system’s $8000 address.
Here is a video demonstration of the design:
I share this design as free to use. I only ask that if you make corrections or modifications to the design, please share. I could feature the design here and give you credit.