Always put a piece of cardboard in front of the radiator when working around it - as you have discovered, they are kinda fragile.
It might be worth taking it out and taking it to a radiator shop and see what they think - you are going to have to take it out regardless. You might get lucky.
Getbmwparts.com shows them at $292 + $15 in shipping, can't imagine they would not have it in stock.
'11 328! Touring - Tasman on Chestnut, 6spd manual, factory upside-down "i" option