Need part for Evans Dash A/C.Trinary sw.

There is a four prong pressure switch that mounted on the high side of the a/c system.The compressor clutch and radiator cooling fan circuits runs through it.It's called a Trinary switch, part #RV212188.Evans has discontinued this part.Does anyone know of a replacement for this part and why it was discontinued?I can replace it with a Bosch relay it just want be pressure activating the circuits.Thanks Curley