1989 suburban rear heat/ a/c

[smokn03]

Was cruising my 89 suburban tonight and could smell antifreeze. My kid in the back said it was dripping from the roof in the rear. So we headed home,and I took the cover off in the rear. My heater core is no good, so figured it was time for a new one.

Here comes my problem. My rear heat and a/c share the same core. It looks just like the a/c evaporator. But has coolant lines running to it also. And I can't seem to find one anywhere. Is this a aftermarket deal? Any help on finding one is appreciated.