Unfortunately I also found these companies, but nobody has anything for the 03-04. Yes, strictly track bike. Street too dangerous.:coocooWell more googleness also brought up these guys. You might wanna check them out:
But it looks like no-one wants to give any love to the 03/04 636's. I couldn't really find any readily available slipper clutches in online stores like kneedraggers etc. Why do you want a slipper clutch by the way? Do you do lots of track time? Otherwise it's kind of useless on the road. Correctly using the throttle would be a lot cheaper alternative!