You can buy Lightning cables from thousands of manufacturers, but Apple Watch owners don’t really have much of a choice but to buy Apple’s $29 charging puck. So if you want a spare to keep in your travel bag (I forgot mine for a weeklong trip once, and it sucked), they’re 20% off on Amazon for Prime Day, one of the only deals we’ve ever seen. It’s even the fancy metal one that ships with the stainless steel Apple Watches.