how to deploy non public App

We have a public iPhone app, to be used by the general public, and we also have an iPad App (we call it the business owner Portal) that has little meaning for the public. When a business signs up with us, they get a password to use the Portal for accessing their business information.

What is the usual way to deal with such non-public Apps (our Portal App)? Is there a way to get this App approved by Apple but distributed via some URL other than the App store? Our Portal is not secret or anything, but since it is not usable by the general public it will not make any sense for people to find it without first talking to us.

I would appreciate your guidance or some pointers to further information.

Thank you.