It was repaired earlier once, my bad luck that I got stuck some how at Usman Engineering Works I&T G7/1 - the workshop market behind Federal Urdu University, and the mechanic welded the slide pins with Copper ( which he should not due to its softness) and on top of it, that idiot had drilled the bracket for fitting the size rather grinding the pins to its size. The misaligned the line of slide-pins and brackets. He should had place the rings on it.
Mechanics had recommend to install Japanese break system at Pakistani Wagon-R which is an eventual end if I failed to find these brackets.
I am trying to source it form Karachi - may God help to find it.
Usman Engineering Works --- NOT RECOMMENDED They don't know the work ever after 30 saala Tajurba ... LOLzzz .....