I was going to say the same thing, it is likely a combination from the transmission gearbox shaft, chain lube, and the breather catch can dripping.
It also looks like you have the 4 speed, which I didn't know the IB still came with those in '04.
I did a series of instructional videos if you care to have a look. Types of oil and such are always up for debate, but I had the same problems when I first got my Iron Barrel (which has almost the same mileage as yours now). A few drops everytime I parked it.
After draining the catch can, changing the oil and filter and replacing the worn-out fiber washers, changing the primary fluid and replacing the primary gasket while in there I currently have no leaks!
I use motorcycle oil in the motor, ATF in the primary, and a green oil concoction in the transmission so now my leaks are color coded. If it starts dripping I'll know that Amber=Motor Oil, Red=Primary, Green/Snot=Trans, and Black=Oil Catch Can.
You can find my videos in this link:
http://www.enfieldmotorcycles.com/forum/index.php/topic,18378.0.htmlGood Luck!