Almost all for the past many years use plastic tanks and crimped fins. Your mechanic is old school and is dreaming of a brass or aluminum tanked radiator. It is true that old Benz used them but they were VERY old Benz and probably won't be found in a junkyard.

I replaced the radiator in my 1983 300CD about 3 years ago. I bought a Nissens on-line. It is a Danish company. The radiator fit perfectly and cools very well. I suggest you do the same. Cost was very reasonable. If you replace yours with one from a different model/engine you may run into physical fitting problems.