I’ve been curious about this computer for some years, and bid on one some time ago, but at more than 600 € that was more than I was going to pay for it.
As far as I know, the machine is internally the same as the PB-2000C which I do have, just with different key labels and a different ROM.
There is an emulator for Windows here: https://pockemul.com/
There is even a Prolog ROM, but again for me it’s not worth the going prices: https://www.casio880.com/categoria_productos/casio/ai-1000/
I wanted to build myself a modern version of this based on the Planet Computers Gemini (https://www.www3.planetcom.co.uk/gemini-pda) which in theory can run Linux, but I’ve had so much trouble with it (running Linux) that I had to postpone it until I can find some time again.
Edit: the video description includes several interesting links including Pocket Emul.
I’ve got the Prolog ROM for it. It works, though you won’t be doing any large projects in any language on it. But it’s fun to play with.