Hi there,
a couple of things to consider for you. When you import from other EU countries, the savings could be quickly eaten up by costs for shipping, paper works etc.. There is also a considerable risk in case the bike is not in original condition. The changes applied may not be allowed in D and you would have to do additional changes to receive the registration. As another source for buying you could try ebay or ebay-kleinanzeigen. Usually there is quite some duplication going on, but maybe you are lucky and find a few more.
Cheers
Richard