I made one that is 31.5. Thru frame wiring. The sack is for storage. Not operations. The thing that looks somewhat like a water bottle is the superior cell battery. It is all open source. No dealers required. Zero in to see the wire from the battery to the motor.Hmmm......class 3 and under 40 lbs. Might be a challenge.
There’s a Trek Domane+ HP, carbon frame road bike, 37 lbs, Class 3 but it’s around $10,000.
Maybe one of the Cannondales, their bikes are fairly light.
Another point too, removing the battery before loading can bring down the weight.