As suggested by forum user Al Hill, using a 6pin PCIe Power cable Adapter will allow you to take advantage of the Molex connector located on the power supply.
I'd really like another solution for powering the GPU, not using the Molexes.
I found another P4000 Family configuration guide and there's a Chassis Maintenance kit / Electric Spares Kit (Product Code: FUPMESK, MM: 915653, EAN: 00735858236003) that as 2x GPGPU power cables, one 2x2 pin header to one 2x4 pin header & one 2x3 pin header which are 1100mm in length.
Can you please find out whether these GPU cables can be purchased separately or do we have to buy the entire kit which has quite a lot cables that we don't require?
To answer your question, the cables are not sold separately through Intel distribution. If you are looking for that specific solution we recommend getting the complete kit.