Depends if you want British or US.
Tenmille good for British, Gauge 1 strictly - as per the handrail on the tender in my avatar if you can see it.
Roundhouse, or PPS do a much fatter handrail with knobs that have threaded backnuts, as on my blue and yellow battery diesel.
Not sure about where you get the US stanchions with the big set-off - might have to talk to Steve the Shop at back2bay6.