I don't know if it will fit your bike, but Acerbis has come out recently with this one. As soon as I can confirm it will fit my 2002 520 EXC, I'm getting one. Its seems to retail for $250.
PDF of Acerbis Fuel Tanks with Part Numbers
Acerbis Fuel Tank PDF
See also threads here on advrider.com
and on KTMtalk