I don't know what sort of connector there is on the keyboards for these machines but on my 'HPC' project I'm using an Eee PC keyboard via this adaptor:
https://www.tindie.com/products/CRImier/eee-keyboard-to-usb-with-firmware-for-teensy20/
A similar principle would probably work for just about any keyboard where the connector is just the key matrix - I'd imagine this applies for most keyboards. Ultimately just connecting the key matrix to an Arduino-compatible microcontroller and setting it to emulate a USB HID keyboard
(as has already been mentioned here
) - Might just save a bit of work as this guy has already designed the PCB and had some made.