Check inside fuse boxes and on the side of your glove box for the code. Sometimes they are hidden there.
Do you know where the car was originally purchased? The original dealer for my 1999 TL was able to give me both the radio and navigation codes over the phone. Or just call another dealer in your area. (Have the radio serial number available also.)
I think there was also a website where you could input the radio's serial number and get the code. Maybe try searching for a radio code thread where that link might be provided.