I think you're talking about one of these (the black part): https://d3nevzfk7ii3be.cloudfront.net/ig...
If that is indeed what you're talking about, it's not a separate part. It's part of the socket that the ribbon cable fits into. Best case scenario is you only broke the black plastic piece and the rest of the socket is intact, in which case you can try to find the same socket elsewhere, pull the black plastic piece off, and push it into place on your iPod. If the socket itself is damaged, however, the proper repair is to replace the whole socket.
Otherwise, look for ways to rig a fix. Put some kapton tape on one side of the cable to provide pressure, slide/press it into place, then some more tape to hold it in place and hope it doesn't come loose.