We don't have a report or export that will display this data in a straightforward way, but if you follow a few steps, you can obtain this information via the Adjustments export (under Analytics -> Exports).
After you download the export for the timeframe you are analyzing, you’ll want to go to the adjustment_type column and filter it to only show 'charges.'
Then, you’ll go to the invoice_state column and filter out all states except for 'Paid.'
Finally, you will go to the adjustment_product_code column and filter out any plan codes, so that only add-on codes are left. This will give you a list of your total paid add-ons.
You can then just use the adjustment_total column to calculate the total revenue received from add-ons only for that specified period of time.