Adding outside team to 1 repo

We are working on a job for an external company
Normally we just add 1 external user to a repo to give them access, but this customers wants access for 5 users.
Is there a way to grant their organisation/team access, or do i need to add each user to the repo?

I guess it should be their responsibility to manage their own organisation, rather than contacting me to revoke some users access e.g.