McGard (the OEM supplier to BMW) has alot of different lengts.
For wheel bolt size M14x1.25 the following part numbers are availible:
27226, 27mm (w/o spacers)
27229, 32mm (5mm spacers)
27230, 37mm (10mm spacers)
27244, 42mm (15mm spacers)
27231, 47mm (20mm spacers)
mcgard.de
You might use the longer 27231 47mm for both front and rear, but check carefully for clearance if you use the longer wheel locks with 15mm spacers up front.