Ok my roommates got a 300e front right (passenger) brake caliper the bolt (with shoulder) that holds the caliper to the steering knuckle. (bottom bolt) if anyone has an extra bolt please let me know asap. Were in Tempe az and i'll drive up to liek an hour if you have the part.
If I'm correct regarding the bolt you need, go to the dealer and buy a set of OEM front pads for about $60. The pads will come with a pair of brand new bolts since those are supposed to be replaced once they've been loosened. Save the pads for when you need them since they seem to last about 40k miles or so.
You should be aware that that's a ridiculous request, to think that you could find a specific brake part in a specific city in the middle of a weekend - but I actually have a couple of them, from a dual piston caliper, which would be a later 300E, not sure if the earlier single piston caliper is the same or not. You have a PM.