How to find book titles in other languages? I received a major task from my professor and I was wondering what approach is academic custom to take in such a case.

My supervisor wrote an article on a certain topic (I prepared already some source material for him). Now he asked me to check which of the (mostly German or French) books in his list of literature are available in English. For those I can't find a translation, he asked for "equivalents".

Doing this my way round would be to check the major library catalogue (like WorldCat) for the authors. This is extremely time consuming even when limiting the languages of the works searched for and I have explicitly been forbidden to exceed the allotted time for my job (it's a financial issue of the university... I will exceed a bit for no payment, but I can't work like 50% over the limit, people would also notice at some point).

Is there anything like a catalogue listing authors' works and their translated equivalents?
Arguably the most complete resource would be the UNESCO's Index Translationum, a database of translation from 1979 onward. 

There you should be able to search more easily, selecting desired language and inputting a keyword from the title or an author. 

There is also a list of references hosted by Michigan State University's Library Guides, which offers a few hard-copy guides for consultation, however these are more restricted by field (mostly having to do with works of literature).