This is a bit of a shocking development for me, too. I never minded when the 12 MP module was shown as discontinued because a perfectly compatible substitute with better specs was available, but no FP3 camera module at all … 
Having said that, while I am quite unhappy with Fairphone’s decision, the camera module is obviously not as essential to the core functionality of the FP3 as the bottom module. – Speaking of essential modules, the latest estimate for FP3 displays is now “the end of April”.
I would strongly recommend to those needing a camera module to use this forum’s marketplace category. My guess is that there are probably still quite a couple of retired functional FP3 camera modules (without +) resting in drawers.
From the discontinued product descriptions (at the bottom of both versions’ pages):
We are still able to repair your Camera at our repair center. Keep in mind that the costs for this repair may not covered by the manufacturing warranty and would require sending your device to our repair center.
If you are interested in following our offical repair process, please contact our Support team.