I went to my second favorite subtitle site and 3 out of the 4 movies I searched for from KLAXXON had french subtitles. They weren't for KLAXXON subs, but I use Subtitle Workshop and Time Adjuster to sync up and change the fps for any subtitles that aren't for the specific movie I need. If you can't find the programs just send me a email and I'll give them to you.
http://subscene.com/Also, I don't know if you watch TV releases, but I was just getting some subtitles for a few TV shows and this website
http://www.tvsubtitles.net/tvshows.html has a butt load of French subtitles for all major shows.