I’m just installing this battery 
on my community FP.
It is a 1500 mAh battery found on the French FNAC website for 7,82€ including shipping. It arrived at 60% of charge this morning. I ordered it on monday 31 Jully, we are Wednesday 4 August.
The temper is said to be at 21 ° but in the room it is already upper.
A piece of cardboard is used at the bottom of the battery in the empty space.
Now the back cover fits well. It a long time since it didn’t fit anymore with my bloating battery.
I have no idea of any protection inside. I hope it is protected against overcharge. My phone is plugged most of the time as a wifi bridge for my computer.
Thanks @Stefan and @Micha2017 for the tricks.
More info latter.