Hazet Tools have them. The one they specifically do for the M102, M103, M104, M119 and M120 is Hazet number 2752. They also have three others in various lengths that will work, Hazet numbers 990-12, 990Lg-12 and 990SLg-12. I have used both a 990-12 and a 990Lg-12 on M103 head bolts.
107.023: 350SLC, 3-speed auto, icon gold, parchment MBtex (sold 2012 after 29 years ownership).
107.026: 500SLC, 4-speed auto, thistle green, green velour.
124.090: 300TE, 4-speed auto, arctic white, cream-beige MBtex.
201.028: 190E 2.3 Sportline, 5-speed manual, arctic white, blue leather.
201.028: 190E 2.3, 4-speed auto, blue-black, grey MBtex.
201.034: 190E 2.3-16, 5-speed manual, blue-black, black leather.