Your best bet is to consult Aviation Week's databases: they keep tabs on most operators and their fleets worldwide. Poke around on the AvWeek web site and you will find a way to access the data (you may have to buy the data). My experience has been that their data is fairly up to date.

Another source might be Jane's. In years past they have published hard copy summaries of civilian fleets: perhaps their information is also available on the Internet.