Here’s some of the hardware I use. For example, the jumbo shopping cart is perfect for large book sale events. And you should always have an auto charger for your scanner in addition to your wall charger.
Two essential items to have are a silicone protective cover like the Proporta Silicone Case for your scanner and a Black Rapid Wrist Strap with FastenR to guard against damage if you accidentally drop it. And by-the-way, the POS-X scanner is the best there is for small and large sellers alike.