The NS250 fork was carried over to the 400, so yes, they are the same. Wemoto list fork stanchions for the NS400, but not for the 250, which is interesting.

http://www.wemoto.com/bikes/honda/ns_400_rf_rg/85-87/

I see you're half a world away, so postage may be a little steep..
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If it ain't broke, fix it until it is.