Here is the part available from another parts seller. The Freeze plugs are 34mm. I suspect the part you need is the same.
Get the part numbers from this listing and ring the forum sponsors. I cant find it on their parts list. It maybe labeled something else. Note that you need to use a small rubber gasket with this part.

I have checked the same plug on my M103 engine. It's exactly the same as the one in your foto except mine is as clean as - pristine (150K Kilometres)

http://www.discountmbparts.com/catalog/?N=11152+4294965652+1668+8479