...from all my reading here, you will need a BMW dlr to
program your new key, regardless of that key source. You can
get a non-authorized key to manually work the door lock but
it will not start your car; thus, not really the option you are
looking for.
From numerous posts here, replacement keys are in the $150-$200
range here in the states, so your local dlr is bumping it up a bit...
and, that your dlr is supposed to do the programming on any
replacement key; they don't come from Germany or anywhere,
already "programmed".
Here's a thread that talks about your situ:
http://www.xoutpost.com/x5-e53-forum/...placement+keys
GL,mD