Mass Import Products to Accounts

We recently moved to Dynamics and it appears Products were not imported for existing accounts. We need to be able to track which Accounts have which Customer Products. I know can manually add a Customer Product, and can mass update data regarding those CPs that have been added, but we have 4-5k Accounts that need this data.

Is there a way to mass import these CPs the Accounts? I've tried tackling this from the CP side as well as from the Account side, but have not been able to find a way to do this. 

Thanks!