Applie I phone 8Plus

We are other end users, not Apple, but I have never seen any refurb products in an Apple Retail Store. I order any refurbished Apple devices I need directly from Apple's online Refurb store:

Certified Refurbished Products - Apple

If you not in USA you might find others. My UK version of that refurb site has iphone 8 but not 8 plus.