Is there a way to bill for drop-ins separately?

We have some members that are part of an unlimited fitness class membership and are marked as no-charge for drop-ins. However, we have more programs and classes that we offer for an additional charge. We would love to have a way for those members to drop-in and pay for the additional class. It would be super helpful if wihtin the settings of the class if we had an option to bill all that register for the class drop-in, even if their settings under tuition has them marked as a no-charge for drop-ins.