Kersonan,  It looks like the rail kit for the 15 KMM is part # H1233, or depending on your region it may be CJ817.  Let me know if this helps.
I've picked up one of these,  in pretty good condition given its age.   it has the inner rail section.   but I require the rail segments that attach to the cabinet in order to mount it in. Anyone know where i can get these,  or even what type of rail is required. cheers.
looking for rails for a Dell PowerEdge Rack Console KMM 15FP