In order to rebind Quick Save and Quick load, you have to install AutoHotkey and create a script.

1. Download and Install AutoHotkey https://www.autohotkey.com/download/
2. Right-Click your Desktop and select New>AutoHotkey Script
3. Name your script whatever you would like
4. Open the Script with NotePad
5. Delete everything in the document and put in these two lines

<key you want to use>::f5 <key you want to use>::f9

Example - I have mine set to 5 and 6

5::f5 6::f9

6. Before you start your game, run the script

Now you should be able to use any key you would like to Quick Save and Quick Load.

Remember, this script is system wide so if you use any other application the script will still be turned on. You will have to manually go down to your system tray and either Pause or Exit the script.