Nick here from Shopify. Good question!
There are a couple of different eBay import apps, but they might not all have import abilities from others (affiliate style), but more about importing your inventory. I'm not entirely sure if some of these apps have the ability to import other inventories to your store, but it could be worth looking through them and even reaching out to the app developers directly to find out more and if it is possible. Let's take a look at some of the apps from the Shopify App Store below:
Hope this helps and if it doesn't answer your question directly at least points you in the right direction!