I think your only hope is to find the part # of the square r/c axles and search google/ebay for them. (Have you still got the packaging for them?)
Failing that, go back to stock parts which should be much easier to source. A pain I know, but may be the only option....
Fusion Hobbies / www.horshamrc.org
The wife stops me being sane and the r/c stops me from going insane....