Wacom Bamboo Ink is an excellent alternative to the Surface Pen | Windows Central
Wacom Bamboo Ink Smart Stylus pressures Surface Pen, others — Surface Pro Artist
Amazon.com: Wacom Bamboo Ink-Active Stylus (2nd Generation, with 4,096 Pressure Levels for Natural Writing & Making Notes on Pen-Compatible Touchscreen Devices with Microsoft Windows 10), Gray : Cell Phones & Accessories
Amazon.com: Wacom Bamboo Ink Smart Stylus Black Active Touch Pen Stylus for Windows 10 Touchscreen Input Devices Surface Pro - CS321AK : Cell Phones & Accessories
Amazon.com: Bamboo Ink Smart Stylus for Windows Ink Second Generation CS323AG0A : Everything Else