Thanks @oshpark for these PCBs:

This is a clone of 64KB cartridge - I disassembled one of those to trace wires:

But my clone is for modern EEPROMs AT28C256 (pin 1 is A14):

Memory chips are completely independent, so one 32K could be inserted instead of two:

UPDATE: full 64KB setup was also tested:

UPDATE2: it looks like you can also put there smaller EEPROM 28C64 (8K)

Link to order your boards: https://oshpark.com/shared_projects/vnBQjk6B