Every year when people start decorating we get MANY requests for an electrical plug with male prongs on each end. We don’t have them. To my knowledge they don’t exist.
Christmas lights have a male plug on one end and a female plug on the other. They are made this way so that you can connect several strings together without running multiple extension cords. You only run into problems if you string the lights starting with the wrong end. The female plug is where you intended to plug the lights in. To make them work you need an adapter with 2 male plugs. The problem is that if you plugged the 2 female ends together there is going to be a totally uninsulated male end somewhere that is live. An extreme shock and fire hazard. The solution is to either run an extension cord to the male plug at the end of the string or take the lights down and redo them starting with the male plug end.