I would not normally post advertisements here, but this evening I found that Gadsden and Culpeper has these shirts on sale for $13. They're calling them the "War of 1812 Battle of Plattsburgh" shirts, and the flag is a little different than the one Grim has up top now, but close enough for my tastes.
They also carry the flag itself, though it's a bit ... well, you can see for yourself.
There's a lot of other Tea Party and generally patriotic shirts, etc., on sale as well.
UPDATE: Does anyone have a picture of this flag? A painting in a book or something? Or do we just have a description? I'd really like to see one.