Change URL of a remote product using a function

Can you advise me, please.
I faced such a problem that deleted products are returned in the import file, and sometimes new duplicates with similar names appear instead of old ones.

I want to implement the following:
When the product is no longer in the import file, then change the URL of the buy button to a different one. But the URL must consist of the name of the product that will participate in the search on the vendor’s site.

There is such a setting in Import Settings, but I don’t know how to insert a function there and what variable to write to it.

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For example:
There was a link like this – site.com/product_351_iphone6
When the item is removed, I need to record another link – site.com/search_iphone6

Do you understand me? The link for each product will be unique, leading to a search on the site by the name of the product that I have specified.`