The Bible Society has a sale on the NA Greek NT with a German Dictionary (the add has a typo: mit Woterbuch, but if you enlarge the photo, das Buch itself has the correct orthography)–only $28.00! (Here)
You can also get a critical edition of Thomas, along with a lot of other helpful literature, from the Bible Society’s scholarly resources.
See also an older post here.
And one more note: if you go to K.U. Leuven, Greek Grammar on the Web, and scroll down, you will find several great German sites dealing with various aspects of Greek Grammar. If you keep scrolling you can find sites in Italian, Spanish, Portuguese, and even Japanese and Korean.