A natural choice for mid quality alloy rim replacements (for OEM products) are from AleRims. In this case we needed a strong rim with a 40mm internal width. The MD40 is the perfect choice. Certainly not expensive, and the quality is great.
We laced the rim up to his Shimano Deore Centerlock hub with Sapim Leader plain gauge spokes and brass nipples, and used nipple washers to be extra sure that the added torque of the e-bike motor would not accelerate rim fatigue (at the spoke hole).