Letterbox Handle

In front of our house, we have a nice letterbox. Unfortunately, one day, I accidentaly broke the key inside the lock (fortunately in the open position). So now, very often, we find the door open ... And, if it rained just after the postman delivered some letters, we also find some water inside! This is not good for the letters.

I tried to remove the lock but, for some reason, I can't. And anyway, when I went to the seller of this letterbox or to a DIY shop, they didn't have this type of lock (note a probably similar one can be ordered - with no guarantee it would be fitting - but it costs more than 3D printing it ...).

So that's why I decided to start this project. It is fairly simple: why not wrap around the right side of the door an object that could:

1. act as a handle to open/close the door (now that we can't insert any key - that was another function of the key - and probably the reason it broke) ;
2. somehow keep the door in a closed position (thanks to a part of the ob