Pop up message on Supplier Site Page

Hi,
Our business wants us to show a message on the supplier site page that the supplier has the federal reportable flag selected at the supplier master level so make sure you check the income tax reporting site on the site level.
I checked for the add content messages but do not see that functionality on the supplier site page.
Any other way to show a conditional message on the supplier site page ?

To make it simple - if the supplier master has the federal reportable flag selected - and the business is editing / creating a supplier site show a pop up message that - check the income tax reporting site flag.