Speaking from experience you'll pay more in Germany when you figure in the exchange rate. Especially at today's rates.
If you still must have one ask your friend to check out the big perfumerie chain "Douglas". There are usually flag stores in the main cities' shopping districts. They should have a few Merkur razors.
What you should get your friend to buy you is Speick shave cream/stick/AS/etc. and/or Tabac products from "Rossmann" or "dm" drug stores. These will be cheaper than in the US.
Also check this thread out...
http://badgerandblade.com/vb/showthread.php?p=2369363#post2369363
for a bit more info.
Good luck.