That should be an available part from any dealer that sells Brunswick boats. Bayliner, Searay, Trophy. They all used that part. The part number is the Bayliner/Maxum/Trophy part number. It is not the OEM part number. If its Perko, which I suspected it was, their part number would be different.
Try the closest Bayliner dealer and, if you're too far, have them drop-ship it to you.