I see,
- Just get some 1 inch flat bar
- Bend in a square U shape to the length of the motor
- Mark and drill the holes for the bolts of the motor, and for the mounting plate on the bike.
- Drill holes in the bike plate
So,
There is a total of 2 U brackets.
Each bracket has 4 holes. 2 for the motor and 2 for the existing plate on the bike.
Or,
Make only 1 U bracket, that will hold both bolts on both sides.
If you do that, you will have to make holes in the bracket for the shaft of the motor. Let me know if you want a drawing of that model.
* The yellow things are bolts, the red is the flat bars.
The brackets are made in 1 piece each (just bend them by hand).