Good luck in finding one of those!
I've been looking for quite a while to no avail.
The external solutions, while not readily available, are much more likely to pop up than the internal solution.
Curtis
I have one of those(the older one without ram), and a Vortex 286 board. My only remaining A500 stuff. They don't work together as I recall.
But you are right, good luck finding it, its in my storage unit and until I buy a home there is no chance of it turning up

I seem to remember someone making something similar to the ICD, but I can't remember the details at all other than it reminded me of the ICD. I was thinking the schematics were even out there somewhere.