Do you have specific interface needs?
Are you looking for pre-made or is kit okay?
I designed some quick extensions and can share the Gerber files if you want to order new PCBs. But you'd have to put then together yourself.
I'm interested by old and new items.
No specific interface need : it is just to enhance my Zoo extension of ZX81 stuff. However, I/O digital extension board to manipulate led or relay will be a mut have for some project I have
Kit is okay, pre made also
Great proposal to share the Gerber file
I haven't yet ordered and built the v2 extension board.
And I found an error with the v1 boards I've been using (flipped A and B side pins)
These work fine as dev boards for prototyping.
But, I need to fix it before I can use them to plug a card in.
Once I've checked that v2 works I'll share the files.
You can use the outputlines with a led and resistance to show your output.