I didn't find any from my usual sources, even Central Valley is made for smaller rail. What I ended up doing was taking C100 flex track and epoxying Campbell's bridge ties to the bottom. What I did was tape the flex to an 18" steel ruler. Then I broke off sections of the plastic ties, about 10 at a time, gluing the new ties in each section as I went, slightly closer than I would on the ballasted mainline ties. Once hardened, I'd move to the next section. This way kept the track in gauge and straight the whole time. Once finished, I white glued wood timbers down each side and epoxied a guard rail made from C70 track scraps I had on hand.