Worksman bicycle wheels are really heavy duty. They lace right in to a simplex hub and use the same size spokes. They are a little wider than the early 1" wide Simplex wheels and work in a pinch. They also accept simplex 26 x 2.5" tires.
The problem with using motorcycle wheels is, where do you stop? Do you use the motorcycle hubs and brakes? Do you try to lace a motorcycle rim to a simplex hub? If you use a motorcycle rim, you can't use the simplex tires. Now you have to find a motorcycle tire narrow enough to fit the simplex frame. More questions?
FWIW, there was a guy building simplex replicas years ago who used the worksman wheels with drum brakes. Here is a picture of one.