I have white DR400T with 36mm forks, full width hub, theres a few things on the DR500T not the same, but good source for 400T headlight, odometer, footpegs and plastics. Tank on DR400 T however is alloy not steel.
The hard part for DR400T are the sidecovers, they were fragile plastic and flew off from new. It seems much harder to get cosmetic parts for than same year RM/PE as no real industry around rebuilding them, Vintage Suzuki white PE guards do pretty well. Motor parts are not such a big deal as plenty of 400S to rob them off.