You will have to buy them as individual spares. The BMW is effectively a re-release of an old body on a TT-01 chassis, the actual complete body kit wouldn't have been re-issued, Tamiya USA show it as discontinued.
To build up the whole body it looks like you would need to source...
#0005455 H Parts
#0115097 J Parts
#1825295 Body
#9495433 Sticker
Won't be cheap!