We present a simple device that works as a secondary source of light with prescribed polarization properties. The device has great versatility, allowing complete control over both the degree of polarization and the Stokes vector that belongs to the fully polarized component of partially polarized light beams. We report experimental results that illustrate the device's versatility, by showing how polarized states can be moved within the Poincaré ball along spiraling paths. © 2015 Optical Society of America.