Check Newjsi.com (Doyle Ploch Sailmakers). They make the OEM sails for Catalina in St. Petersburg, FL. I just ordered a Doyle APC asymmetric spinnaker with ATN sock, tacker, bag, tackline, etc. for about $2100 for my C309, which is very similar to your 310. Their sails are all made locally in their St. Pete loft.