Can one buy a prepaid card for Turkey in Germany?
 

I know this is NOT Germany specific, but I think this might be the best place to ask this question.

I see various Turkcell cards offered on ebay.de, but none of those cards being offered are close to Duesseldorf, our destination. Are such cards offered in any of the LOCAL call shops? I could not find such offers although there were some online offers.

Thanks,

Stan

I expect that you won't find any reseller of Turkish SIM cards outside Turkey since they have very strict laws requiring all phones bought outside the country to be registered by their IMEI and if you use it with a local SIM card to be tied to it (see .:CEIR-Central Equipment Identity Register). Registration costs 5 TL and sometimes they even ask for a invoice proving the phone was acquired legally. Furthermore you may only register one device per year, so if you carry a second phone or a USB modem you're already violating the law.
If you fail to register your phone it will be blacklisted and banned from all Turkish networks within few days up to three weeks at the latest. Once a phone is blacklisted it won't even work with a foreign SIM card.

Despite it doesn't circumvent the obligation to register your phone you might be interested in Turkcell Germany's prepaid SIM card sold in Germany aiming to Turks living in Germany, which does not only offer cheap calls from Germany to Turkey but also relatively low roaming rates for Turkey: Turkcell Europe

Incoming calls (to your German number) are free up to 1000 mins/month (exceeding minutes cost € 0.09/min)
local calls and calls to Germany € 0.20/min
international calls to any other destination € 1.50/min
data costs € 0.42/MB + € 0.49 per day

There's a further Turkish operator offering a prepaid product in Germany as a MVNO which includes cheap rates while roaming in Turkey: TÜRK TELEKOM Mobile - Tarif

Incoming calls (to your German number) are free
local calls and calls to Germany € 0.15/min
international calls to any other destination € 1.29/min - 1.99/min
data costs € 0.30/MB
free Internet access on all TTNET WiFi hotspots in Turkey for 600 minutes/month

Amazing. Even Thailand dropped this arcane provision about mobile registrations a few years ago.