Hi Brian,
I believe the simplest way would be to add a top section with a Label field to the portal screens. In the OnScreenLoad actions set in the Advanced button, you can add an action to put the Entity name into the label, thus showing the client name on screen.
If you click Edit on the section, you can adjust the size of the borders or remove them completely. You can also edit the formatting of the label as well.
Hope this helps,
- Adam