I too am looking for a linen sport coat, and the brands I'm more familiar with (such as J. Crew) don't seem to have them this year. I have found:
John W. Nordstrom Two Button Linen Sportcoat
L. L. Bean Kennebunk Linen Blazer
But I can't find any independent comments on what sort of quality or fit they would provide, or even just general commentary about the brand. Anyone know if they're decent?