In case you missed it, sellers operating a store can find the link to Sell Similar easily in their Active Listings folders.
Pull up your active listings, look for a listing you want to use, click the little box on the left, the Sell Similar button lights up at the top left of your Active Listings. (next to the edit button).
I was able to list a new item using this method, then was able to use the link within the new listing to sell similar again and again with each new sell similar listing. (new listings showed the old sell similar link in them).