Ability to Create an Invoice Line Item for Zero Dollar Amount

I need to create Invoice line items for zero dollar amount from projects.  We're bundling serval items together and billing accordingly.  This would be more for customer presentation purposes and providing additional details as to what was provided.  I'm using Event/Event at the Top Task level.  Zero billing event amounts are not picked up by standard functionality.  Looking for some other possibilities/workarounds.  Prefer to not use Invoice Comments.