Hello Francis,
If you are lookintg to buy pre made railings in that size then I'm afraid you are out of luck!
There are alternatives if you don't mind a bit of work.
Firstly, if you are happy with a soldering iron then you could solder up lengths from two thicknesses of brass wire on a jig and then glue some plastic channel strip over the top and paint it brown to simulate the wooden top rail.
A second opetion would be to purchase stanchions and solder or glue brass wire through them and add a capping rail as above. However you may find it difficult to source what would need to be 4 hole stanchions and settle for 3 hole ones instead. There is a range at Cornwall Model Boats where you might find something suitable like this one:
**LINK**
Have a browse using stanchion as the search term. This is not a cheap solution as they will cost over 60p each! At 1:43 scale you need 27mm stanchions but 25mm will do the job if there is a rail on top.
Sometimes there is no simple solution…
Colin