Kathy, I’m not aware of specific definitions for loan or deposit add-on products. The CFPB defines Credit card “add-on products,” as additional, optional services. You don’t have to buy these or other extra products or services from the credit card company to activate your credit card. This generic definition could be modified to fit deposit or loan products.
Additionally, here is some guidance on marketing add-on products: https://files.consumerfinance.gov/f/201207_cfpb_marketing_of_credit_card_addon_products.pdf