PSU missing 12v 4-pin connector 4 CPU power supply

Suggestions please to rig power for the square 4-pin 12v connection,
missing from the cabling from a CODEGEN 250X-1 250W PSU

Have an MSI KM3M-V mATX board which has the square JPW1 (4-pin 12v)
connector to power the CPU. 2x GND & 2x 12v pins showing.

I don't know why this ATX PSU unit which is only 4-5 years old doesn't
have the square pin for the CPU power supply. Maybe is too old and the
new generation of CPU need direct higher power supply that the 20-pin
socket can provide, but I'm only putting on a Sempron 2400 so I should
be able to tap off 12V from somewhere and run it in with the correct
male fitting.

Thanks
TJ