Quizzes with built in commerce

Hello all - this is my first forum post and so far, I'm blown away by the amount of vital information here. So thanks already for the great community of resources.

I'm currently running an educational program for a non-profit sustainability organization, so our problems seem somewhat specific to what we're trying to do. Without bogging everyone down with all of our programmatic specific, we're looking to charge our participants for quizzes to become certified.

Do any of you know of a provider that offers quiz creation with e-commerce attached to the quizzes? We currently use Classmarker and it suits our needs, sans the lack of commerce, which is understandable, as most using Classmarker or similar have no need to charge for the quizzes. Any direction any of you have is greatly appreciated.

Cheers,
Darby Strong
Sustainability Academy Coordinator