J Brake pads
The EX250J uses the same pads front and rear, Kawasaki #43082-0081. Pads used by club members so far include Vesrah and EBC. For other brands, you can follow the links to the manufacturers' sites in the EX250F brake pads article to find the part numbers you need.
Vesrah part numbers:
For Vesrah pads, see kurveygirl.com
EBC part numbers:
One of our racers found the sintered Vesrah pads on the front to stop better than the EBC HHs. They have good initial bite and great feel, and you can go a little deeper into the corners.
See here for more information on brake pads.