Where can I find handle-operated flushbolts for French doors?
As far as I know, what you're looking for doesn't exist as a flush bolt.  If you think about it, you'd need to do quite a bit of woodworking on the door in order to install a mechanism that actuates rods at the top and bottom of a door via a handle in the center.  This type of arrangement DOES exist in surface bolts, where the rods connect to the door externally -- think commercial door hardware.

However, there may be a different way to accomplish what you're trying to do: Automatic flush bolts.  These are actuated not by a handle, but by lever that is pushed on by the other door when it's closed against it.  Then, you could use a dummy handle on the door with the flush bolts, and that door will swing freely when the other door is open.



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