Almost anything is repairable it just depends if you feel like spending the time. You'd need some fiberglass cloth, resin, and sand paper. Also you'll need to repaint it. To me that would seem like a lot of work for something I can buy for $30-50. The last time I trashed a cowling I just got a new one but that's just me. If you enjoy fixing stuff and are good at fiberglass then repair it. If not go get a new one and bolt it on (and go flying).