Not 100% sure which antenna you need but there are generally only 2 common types of connectors. You should be able to put on any antenna you can find that will screw on. Look closely at the center pin and the type of threads and compare those. You should be able to find a antenna that is designed to go onto a router that will fit.
Now if you mean you damaged the connection on your device or you damaged something inside the machine that is extremely hard to say if you can fix it. If there is a small wire going from the external connection to wifi card then that you might find a replacement for. If the jack is built into the motherboard of your machine then it is not likely possible to fix it.