K-Line remade 10" straights. They made 27"R curves and 36" straights which were never made by Gilbert. After Lionel purchased K-Line the 27" curves were included in several Lionel American Flyer S Gauge sets. There is so much original Gilbert track available there is not really any demand for repro Gilbert style track.
The challenge in S gauge is turnouts. There are none made that are the original Gilbert style wider than 20" radius. Decades ago GarGraves made some #5 turnouts but not many were produced. Prior to that ROW made some #4,6&8 turnouts using GarGraves rail but they are almost impossible to find. Lionel S gauge FasTrack turnouts can be used with Gilbert track because there are adapter track sections available but they do not look the same. S gauge FasTrack turnouts are made in 20" and 27" radius versions.