Air Conditioning Retrofit: Installation & Costs

Hello, I want to retrofit a manual air conditioning system to my Golf IV TDI (100 hp). I already have some parts together (only VW parts). Now I'm looking for the electrical connections for the compressor and pressure sensor. The VW dealer couldn't find a specific wiring harness either. Does anyone know if all the connections are already in place, or what I need?
Thank you. I will also provide information about further success.
Best regards, Tom.