The person you spoke to at the dealer is either lazy or incompetent. The ETK (used internationally by all dealers) can show any part for any country. Here is a sample kit listing for the reversing camera.

Actually obtaining the part may be somewhat more difficult. There are 3 major classes of parts:

1) Parts normally available in the US, and already priced and in the US system.
2) Parts not normally sold in the US, for which the price will show as $0.00 - these will require the part be added to the US system by BMWNA.
3) Parts which have been determined (perhaps in error) that they cannot be sold in the US (euro versions of first aid kit, fire extinguisher, warning triangle, and so forth).

There's another category (which almost nobody will encounter):

4) Parts which require a VIN to order, and the VIN must be confirmed by BMW AG. These are generally either Individual parts or parts from the racing catalog.

Anyway, back to your original question - if you can post or PM me with the part number(s) of the retrofit kit you're looking at (best), or what model (be specific, like 325xiT) and production year and the complete name of the kit you're looking at, and I'll pull up the kit contents and post the part numbers for you.