There are black belts available as well as the clearish ones. I found that the black ones "feel" more flexible when handled. They are supposed to be quieter some report. My listening room/head/ears are too noisy to be sure of that. I think VPI supplies the black ones on all tables now.
McMaster-Carr carries custom made o-ring/drive belts in a variety of materials.
McMaster-Carr carries custom made o-ring/drive belts in a variety of materials.