You sometimes see ex-display products in stores like Currys - I think they call them Managers Specials. But if they've been on all day for the past 2 or 3 years then your mileage may vary as to what state they are in.
I got a second hand Lenovo laptop on Ebay USA - because I like the old keyboards they used to make. It was a five year old laptop but it had SSD and a fast chip in it. As long as the pictures are clear and the seller feedback looks okay Ebay can be worth a look.
Also Amazon Warehouse deals (products that were returned or the packaging was unsuitable for sale) often have good stuff - as long as the condition is listed as very good.