Sell a virtual product, ie an access code number?

I am using Moodle as my LMS for our training site. I want to have potential students to be able to pay for classes by buying an access code number. They can then take that number and enroll into a class when they are ready.

I'm not "married" to this model, but I can't think of another way to allow students to easily pay for, and take a class. Moodle is great for setting up and managing classes, but only set up to easily take "PayPal" (PP). Many students would like to pay with credit cards without having a PP account.

I know of a few sites that use ZenCart to pay for classes, and use Moodle to manage them. I've asked for help, but so far no response.

Any suggestions?