As far as I know they do make one for the kx250.
There many euro pipe builders that have stopt making KX500 pipes, and some are now making only 4-stroke pipes.
HGS is still in the bussines of two-stroke pipes. Maybe the still have a factory pipe from The Groot.
It was till last year Kawasaki's World Factory team, and HGS made all of there pipes because it was next door.
If You need a translater to Dutch(Holland/The Netherlands). Reply or PM Me Maddog or azrazer,or any one that needs to.
Dutchie
Ps. The pipe on the AF is from a CR.