I was just talking about this with my local Nacra dealer (atlanticboatandsupply.com). You can buy the 500 sails. Just contact your local performance catamarans dealer, or you could try contacting http://www.performancesails.com/, they are the company that makes the new sails. Did you contact whirlwind or just look at the website? I am surprised they won't build you a sail. EP sails would be a good choice as well.