Hi there and welcome
There are a number of page sensors for this printer, if you look at the following link you will see there
Brother MFC-9460CDN MP Paper Empty/ Registration Front Sensor PCB Assembly
Brother MFC-9460CDN T1 Registration Front / Rear Sensor PCB Assembly
Brother MFC-9460CDN T1 Paper Edge Sensor PCB
I could not see from your description which on you were referring to but these are all sensors available
The link is here
If you would like any additional information or assistance, please do not hesitate to let me know.
Else if you can take a second to rate my service by clicking one of the stars at the top of the screen then submit, that would be greatly appreciated.