Yes! XS Plain Steels are available here: XS Plain Steel Single Strings | D'Addario (daddario.com)
XS Plain Steels are Nickel-Plated instead of Tin-Plated and then treated with the XT dispersion coating, making them our longest lasting plain steel strings available. They are made with our proprietary NY Steel for added break strength and feature Fusion Twist technology for enhanced tuning stability.