The difference in the two reamers is their diameter and length. The old loop plugs were fatter than the later pin type plugs. I would recommend Samstag Sales for a reamer
http://www.samstagsales.com
They sell a full line of German tools such as; Stahlwille, Hazet, Heyco, Gedore and also have a very comprehensive list of MB factory tools with MB part numbers. I think that link I inserted is the correct one, but if not, do a Google search on "Samstag Sales"