[hakfoo]

If money is no object, the closest you can get is a "Beamspring" board from a '70s IBM terminal.

There are adapters you can bolt on to make them speak USB, but a lot of them are a significant effort of cleaning/derusting/repairing since many of them are "barn finds" in iffy condition. A nicely restored one will be in the 1-2k range.

I wonder if an alternative would be to take an actual Selectric, which are likely cheaper and more available, and tap into some part of the mechanism that parses the keystrokes and convert that to modern signaling. I could imagine a comical assembly that's basically one of the old typeballs with a few dozen contact switches, all wired to a Bluetooth keyboard module