I believe the plastic key is called the "spare key" with part number 51218213932. $40-$60 probably, if you can find it.

I also think it has the EWS chip in it to make it fully functional, although being made of plastic it would wear out more quickly than steel.

Even if AAA could cut you a copy, it would not be able to start the ignition since it would not have the EWS chip.

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2001 X5 3.0i, 203k miles, AT, owned since 2014