There are a bunch of different upsell and cross sell apps available in the app store. Below I have compiled some of my favorites that I recommend checking out!
I hope this helps! If there is anything else I can help you with, please let me know.
Very excited to recommend you OneSell App. In OneSell App you can Sell more with our proven upsell & cross-sell pop-ups. It only takes a few minutes to quickly create an Upsell offer for your store that entices website visitors to purchase two of the same product. You can create collection-wide offers or break it down and create something unique for each product. You can also set the offer to appear when the product is added to the cart or at checkout.
Please check it out: https://apps.shopify.com/easy-upsell