In ten seconds of google searching I found a Wave main from a respectable loft for less than the Hobie stock sail.
The Calvert might be a little more, but I'm willing to bet the difference in price it's a whole lot better value than the stock sail. And it's probably made in the US instead of by slave-labor in Malaysia or wherever.
The mains that I quoted are on a website affiliated with the IWCA.
And if you want to support labor in the U.S. All Hobie rotomolded boats (sail/ kayaks) and sails (other than euro boats) are made here in the U.S. There used to be about 20 boat manufacturers here in CA, Catalina, Cal, Capitol Yachts, Hobie, Performance, etc. Now there are only about 3.
