How do we search out creators who allow commercial use of their designs

I don't think there's an option to filter models by license type. The only exception to this is editorial license, which you can exclude from the search if you don't want legal issues with purchased models. On the other hand, if you're making, or planning to make business by selling printed models, then consider commissioning artists to make bespoke models for you - not only you will have all the rights to the model, but you also will be given opportunity to pay a more fair price to the people from which work you want to benefit. I mean most 3D printable models on this site are selling for $5-20 which is ok if you use models for personal needs, but kind feels like stealing if your aim is to use the models commercially.

There may be artists that are willing to negotiate a custom license with you. So if you see something perfect, it might be easier to negotiate a deal with the artist, rather than commission another artist to do something similar.