Micro Engineering makes ONLY nickle silver flex track. In N scale, they make Code 70, Code 55, and Code 40. They also make No. 6 switches in Code 70 and Code 55. If you got brass track, ME didn't make it.
Although Chulvis doesn't handle it, I've had no trouble getting supplies of the Code 70 from George Canham at Wig-Wag.