To answer your main question: I believe that cruise insurance is designed to protect the cruise line as much or more than it is to protect you.
The site that Phil & Liz mentioned is a good one to find and compare different, independent, travel insurance policies. Make sure that the company has an A rating or better.
Medical and Medical Evacuation are the most important parts of cruise insurance. Losing the cost of your cruise will not cause true financial hardship. You have already paid for the cruise and all you are really out is the joy of going. It is terrible but not catastrophic. A $100,000 + medical evacuation and foreign medical care will cause severe financial hardship.
I'm not saying forgo cruise reimbursement insurance but make sure you have the medical and evacuation.