Let not just Google, but also gamba, be your friend. You are looking for a 4-chip ROM card, anyway.

I'm not aware that there was a parity variant of the IIsi, as there was with the IIci, but it is possible. Look at the chip speeds on the 9-chip 64-pinners. It is conceivable that they were RAM cards made for PCworld printers, which guess might be clinched if the chip speeds are low (eg, 100ns and up).

de