There will be a whole other set of ecommerce search intent keywords that focus on words like "buy", "buying", etc. -- best way I found to find them is pick a product keyword you're trying to rank for, let's say "smartphones". Google that keyword, find the first retailer who ranks for it (ignore brand sites for now like Apple, Samsung, etc. ). Get that retailers URL and punch it into SEMRush or ahrefs and look for all the other keywords that page ranks for. Start scrolling through list and looking for modifiers e. g. "buy", "purchase", "shop", "free shipping", "discount", "coupon", etc. And start copying them down