Needing information on 69 key in, lights on buzzer

I guess it depends on how correct you want it to be. You likely can get "the wrong one" and the mating connectors out of the yard (let's say) then unpin and repin the connector terminals with your existing wiring so it plugs in if necessary.

These are not that complex. The buzzer section is well.....a buzzer. If you have to, get a couple from the yard, and pry one open. You can easily deduce the circuit by looking and with an ohmeter, and maybe a battery