Anyone know where to get a 'blocking relay'

I have a 71 with A/C. Does anyone know where to buy a 'blocking relay'? Mine was missing when I bought the car. I can wire around it, but I would rather have one in place. This is the relay on the right side attached to the heater box. It works with the anti-diesel relay. I have looked at the popular sites, but can't find one.

You may have to take it apart and find out how it works. Then get a standard Bosch type relay and wire it in place. All a relay is is an electrical switch controlled by something else.

I'de look at the flea markets of the major corvette shows, I found mine at Carlisle years back, and for only $5!