question in the title, I need a couple replacement castle nuts for my steering like the pitman arm any help would be appreciated.

http://www.apexfasteners.com/
the first I don't know if they will sell in small qty.

http://www.pointe-products.com
Point products sell both castellated nuts ( They call them sloted nuts) and prevailing torque nuts which are ok to use also.

http://www.fastenal.com has both