Call a Mercedes dealer or go to the yard. Shipping will be more than the bolt. It may be easy to find once you have the PN.

Getting these bolts out is the same as the striker bolts in the door. Also, I don't know that the FSM calls for locktite. Look it up before reinstalling.

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85SD 240K & stopped counting painted, putting bac together. 84SD 180,000. sold to a neighbor and member here but I forget his handle. The 84 is much improved from when I had it. 85TD beginning to repair to DD status. Lots of stuff to do.