Someone please correct me if I'm wrong...
There are 2 versions of the Keihin PWK38 Quad Vent Air Striker carb, the AS1 and AS2.
The AS1 fitted to earlier bikes and the AS2 fitted to later bikes, they're very similar carbs.
The AS1 has a black 'screw on' top...
AS1.jpg
The AS2 has the top secured with two screws...
AS2.JPG
Your 2004 bike should have the AS1.
Where do you live? I can recommend this shop based in Holland (they ship worldwide) for Genuine Keihin new/used carbs and spares:
Frank MX Parts
https://www.frankmxparts.com/
Hope this helps, Dave.