These are encoded keyboards, ASCII with PS/2 or USB encoders.

I'm looking for a 4x5 matrix, if it's a keyboard, or a raw switch array.

Unencoded keypads were available everywhere a couple of decades back. Now, however, that doesn't seem to be the case. Mouser offers only full (84-key) keyboards, all encoded, in any case.

I have several pieces of equipment that I've been using constructively since the '70's that use a 9-wire cable common to all these devices. That's just the wires needed to encode up to 20 keys, though mine uses only 19.

An important feature, of course, is that it has what was once a "standard" key layout, i.e. a 4x4 square matrix of keys ranging from 0 to F and a left-arrow, a right-arrow, and an ENTER key.

RE