If you foresee this type of thing happening regularly, you might want to create a dynamic sender profile for cases like this, where the From Name and From Email are set to variables in your data source.
For example, set your From Name to be
%%From_Name%% and your From Email to
%%From_Email%%, then make sure your sendable data extension has those fields set to whatever custom Name/Email that you wish from your organization.
Your RMM should still allow replies to go to a specific inbox.
Lastly, Marketing Cloud prefers you use Verified email addresses so that any addresses on whose behalf you're sending mail have the opportunity to verify this permission. You can manage these addresses now in From Address Management.