Even with the best search functions, at some point a customer will search for something that you don’t have.
Most webshops will offer a no results page asking the customer to continue shopping by going back to the homepage, but it tends to be more effective to navigate the customer back to your webshop.
One way of doing this, is by displaying recommendation sliders. Since it’s likely that the customer has already browsed around your webshop (at least a little bit) you could use their click history to show other products that may be relevant to them.
Use recommendations based on browsing history if no results match their query.