Joe, do those handrails fit in the holes of the walkway they were originally attached to?
If they do, but not into the other walkway then the problem is clear - the holes in the "new" walkway are smaller. If that is the case, since you can't drill square holes, and enlarging them by other means would be challenging, you will need to reduce the size of the of the rectangular ends on the stanchions. You could likely do that by taking off thin slices of the stanchion ends.