Intel D945GCZ where do I get an on off switch that fits into the 9 pin connecto

Check the open pin positions on the dell case connector. They can hang out off of the Intel board power switch cluster of pins. You only need the actual pins with wires making contact with the power switch cluster. Try the dell case connector in different positions on the pin cluster until all the dell case lights work. These are all low voltage and having the pins out of position until you find the right spot isn't going to hurt the board.

It sounds like you put a new motherboard into your dell case. Most dell cases have hard plastic cluster pack which only fits the board they came with.
If this is the case you have two choices, you can cut off the plastic cluster which will leave the bare wires which should be color coded. Next visually trace the colors which go to your case power switch as these are the minimun you'll need to start the system.
You're going to have to solder or wire connectors to the ends of these wires (2) to hook to the motheboard pwr switch. You can get these at an electronics shop or by removing them from an old case.
If you just can't wait the short cut is to jumper or short these two pins on the motherboard which will start the power supply, system shutdown will turn it off for you. good luck