It doesn’t exist. Unless you make it from their double track. Decide on which of the two radius you need and score along the bottom with an exacto about 5-10 times. Make sure you cut through the three ribs fully, once you’ve scored it, carefully snap the track in half and bingo, single track. There will be a white line where you snapped the track, but a little sanding and ballast will take care of that.
I just slipped thin strips of Evergreen polystyrene under the outside rim of the ballast on my Kato single track and it worked well.
That’s what I had before, but I like the look of these curves better. I have the double track curves on other areas of my layout and the trains look great going through them.
