Lazy Jacks
I purchased my Cat 30 with the Sail Cover and lazy Jack cut-outs already installed. The PO had used a great canvas shop, however the guy left to pursue a career on Wall Street. I would imagine that any good shop would be able to fabricate a Cover for you. Mine uses velcro to close around the Lazy Jack's lines, and nearby are twist studs used to secure the cover around the Boom.