We sell Renthal Enduro High bars (used to be called Dakar Highs) - see
http://www.totallyttrs.com/#High_barsThey are the tallest of the standard 22mm Renthal bars and also a bit wider than most. I put them on all my bikes and they are a great encouragement to get up on the pegs!
Regarding longer cables, I supplied new standard length cables for the TTR250 and the WR250R to Venhill and they make up sets for us that are an excellent match for the originals.
If you are just going for the higher bars then it usually possible to get away with the standard clutch cable but throttle cables can be too short. They often require turning the throttle upside down to get some free play plus maybe routing the cables differently.
If you fit higher bars
and bar risers then you almost certainly will need longer cables.
Brian