My dealer provided the locks for my ML when I upgraded to the chrome OEM wheels.
But for aftermarket locks, I went to tire stores...I would recommend McGard locks if you do purchase any at all.
2009 ML350 (84K) - Family vehicle
2001 CLK430 Cabriolet (71K) - Wife's car
2005 BMW 645CI (124K) - My daily driver
2012 Mustang V6 (60K) - Daughter's car