I always use this particular site for currency conversion it's a "realtime" one and does the conversion for you as the exchange rate varies.
http://www.gcitrading.com/converter.htm
I would have thought that your banks would do currency exchange for you?
I paid for all my ADR at the Alphaklinik on my credit card. I had to increase the limit on it of course but the Alphaklinik were happy to have credit card payments. It could be a good idea to e-mail the finance administrators at the Alphaklinik to see if that is still possible? However the dollar taking a dive at the moment it could be a good idea simply to buy Euros straight from the bank
Best,
Alastair