I swapped out the aftermarket seat that was on the bike when I bought it (see sig pic) and installed the stock seat for wife's comfort. The stock seat does not have a rear flange to screw into the rear fender, is this a missing part? I can probably rip it off the aftermarket seat and attach to the stock. I tried searching the net for a picture of the rear fender attachment on a stock seat, but couldn't get a good shot.

 

There should be two bolt holes at the rear of the passenger pillion. There is a metal tab that bolts on and extends to the mounting hole in the rear fender. Older ones would just have a hole to insert a bolt into the fender, newer ones have a spring mounted bolt attached. I'm sure they are available from harley or you might get lucky posting in the parts wanted section. Newer models (maybe 2007 and newer) are a little longer than the ones from earlier years.

 

I've got one of the tabs from my 04 that's been laying around and I don't need. Drop me a PM with your address and I'll send it over to ya.