It would be most effective if I went at it in drag... aside from the most extreme female veiling, most other "Muslim" attire is actually rather ambiguous, I think. But a black habit with an eye slit, I think, tends to be seen as "clearly" Islamic dress. Maybe a Saudi 2-generations-off-the-camel-farm type robe would do, but I'm not sure even that would certainly make the point. A star-and-crescent armband, à la King Christian?
(I don't see kufis as "clearly" Muslim garb; in fact, there are a couple Baptist preachers here in Seattle who wear 'em routinely.)
Any 'catters thinking of participating in this or any other 9/11 stuff this year?