Checking daily, I have searched EBay for the term: "BMW Sirius". Then I sort the results to show newest on top. Today, finally, I got a hit with a valid part number. $399. I'd have liked to find one cheaper, but I bit the bullet. I ordered the bracket and hex but/bolt from bmw of south atlanta.
Once I install it this weekend(provided it arrives by then), I'll reach out to bimmertech for the remote coding/activation. He emailed and told me he can do this, although, technically speaking, I'm not sure as to how that happens.