Ok Max, any crank with a sprocket attached could be put on the left side and the right side rear and cut the pedal arms off. With aluminum ones it would be easy to make them look nice. That takes care of the motor drive. Then you can use the freewheel cranks from SBP on just the front bottom bracket.
Sick Bike Parts LLC - Performance Parts for Your Motorized Bicycle
You will need the crank arms, Hvy duty freewheel. Your choice of sprocket and the spocket mounting hardware kit or just goto the hardware store for 5 small bolts cause you will only need one front sprocket.
The rear wheel freewheel will take care of coasting, the front so the pedals don't spin under motor power and the motor clutch will do if you have to pedal power. GL