3rd party courses - limited seats

Summary

How to limit users who access courses

Content

We are looking at doing a small rollout of 100 users (first come first serve) who will have access to a 3rd party vendor course (either Skillsoft, Service Skills or both). It is my understanding that there is no way on the vendor side to limit how many users access the course once we load it into the Learn Center and if we don't restrict the number of users we will get charged for the extra users. If anyone uses either of these vendors, please correct me if I'm wrong.

So if my first assumption is correct, what is a good way to restrict the number of users who can access these courses?