- https://app.oberlo.com/explore

  https://www.aliexpress.com/all-wholesale-products.html

+ https://autods.com/blog/ebay-variations-listings-vs-single-item-listings/

- https://waxpackhero.com/blog/simple-guide-to-creating-an-ebay-variation-listing

- https://www.ebay.com/help/selling/listings/creating-managing-listings/creating-listings-variations?id=4150

  You can create and manage your variations through the advanced listing form, or Seller Hub. 
  Each tool will walk you step-by-step through the process.

- https://www.ebay.com/help/selling/listings/listing-tips/using-advanced-listing-form?id=4159
  

  To start adding the variations (aka the "child listings"), 
  you will need to select the "edit" button on the eBay tab of the listing that you want to add variations to. 
  Once you select "Add variation" a dialog box will appear as shown below. Fill out necessary information