My assumption is something like the google shopping feature. This shows the product you're looking for at all available sites in your country so you can purchase the cheapest one.
I've been using Kagi assistant for this for quite a while. I just run a query with some variation of "Compile a list of online stores with shipping+price, sorted by the average user review score of the entire site, sub-sorted by price where I can buy $foobar?" sometimes I have to give it another push to tell it options or where to look, but this works pretty well for comparison shopping.