yes the metal handles are indeed supposed to be magnetic. the handles have a lifetime warranty so feel free and use that. not sure about the plastic ones ifixit sells in the cheaper sets. if you have a magnet that can fit into the shaft you can fix it yourself. glue it in with a bit of e6000 dont use too much or youll glue your bit in place. leave it assembled for a day for the glue to set.
what you need is a usb cable. its a USB 2.0 mini-b standard type. this simply means its a USB 2.0 mini-b to USB-A cable. (with usb a being the part that connects to the computer or ps4 or 5 volt cellusar charger. and the mini-b connecting to the controller.
