You could try the SDX based cart here, which contains an option for MAC/65:
viewtopic.php?f=4&t=1391Alternatively, I took the v1.02 image from here and just repeated the binary 8 times to make an 8Mbit image:
viewtopic.php?f=2&t=1685The latter should work as I don't think it 'disables' the cartridge (which would require a different address)