Unusual Rotary Encoder Output
Apparently, that encoder has built-in circuitry


to debounce the signal edges;
to detect the direction (by reading the state of the other line when an edge happens on the first one); and
to generate a short pulse.


Nowadays, all this can be done in a microcontroller, so it is unlikely that a direct replacement is still made.

It would be possible to build your own circuit to do this (with RC filters, logic gates, and a monostable (555 or 74xx123)), but a microcontroller board might be easier.