Shorter Lug Nuts?

i bought aftermarket rims for my SL (R129) these rims were designed for the SL, but they had shorter lugnuts that came with them original. well i bought these used and the seller didnt have them. they are Antera rims. right now my lugnuts are too long in the back and they hit the brake caliper's. i need to loose between 10mm and 15mm. i bought a set of 15mm spacers BUT with those on, the wheels stick out too far and the tires rub the quarter panels.. is there a company i can buy shorter lug nuts from? and if so, what are the size of my stock lugnuts?