Elias here with Shopify Support. Thank you for reaching out!
I understand you're looking for an app that allows you to offer add-ons on the product and cart pages. Just to clarify, add-ons for each product will typically appear under the line item of the specified product. With that said, were you looking to create add-ons that don't need to be created as separate products as well?
If so, I'd recommend using Infinite Options or Infinite Product Options. However, since they aren't separate products, I'm not sure if you can add this to the cart page. If you'd like to offer add-ons on the cart pages, then you may need to create them as separate products. Both, Upsell Product Add-Ons or Product Addons, can show add-ons on the cart page. If you need any help with these apps, you can always reach out to the developers directly through the contact information found in the Support section of their app’s page.
Let me know if this helps! If you have any further questions, don’t hesitate to let me know!