Here I post my motor mount.
It is cheap, 3,80€ of materials and an hour of work.
It is composed of 2 parts. The aluminum one is 2cm thick and lamps to the truck, you need to have muscles to tighten it good and it doesn’t move.
The second part is a 4mm thick steel plate with slots for adjusting the tension on the chain, and the holes for the motor.
I imagine there are a lot of this kind of motor mounts, but I wanted to share my attempt :).
It is really easy to make and you only need a drill press, a manual metal saw ( or electric if you have one), and dremel.