Yes it is repairable , though I don't know of any kits .
I have filed out the crack on one wheel and filled the groove with aluminium filled epoxy , then dressed it smooth and painted the wheel .
On another , where the wheel was so bad that some bits had come out and the crack was a 6mm gap , I wound copper wire , several times , around the steel shaft that is inside the s/wheel then did the epoxy thing .
A good mid winter job ,, ( read that as , "an exercise in patience" ) ,,
