If you can't get them to do it, then you can always go aftermarket parts. www.bavauto.com
has lots of cheeper aftermarket parts that meet factory specs (if I'm not mistaken) and they are a ton cheeper than the dealerships 700% markup prices.
$600 for a round piece of plastic with 2 holes and a screw top so you can cram a filter in there is friggin redicuous dude. Don't pay for that.
Get one from aftermarket or a junkyard and get a trusted mechanic to install it for you.