Aversis offers these HDR maps for free, only for non commercial use! Note that they are much lower quality than the Full Spherical or Skydome HDRI images. The difference is that the free HDRI’s were made with a ‘mirrored ball’ to capture the environment. Because of this, the photographer is mirrored into the ball, image quality is lower because of the ball’s surface imperfections and the resolution is also much lower.There will also be stretching when mapping these free hdr images to a full sphere because the center of the HDRI has more pixels relative to the outside of the sphere. However with some carefull placement you can achieve good results with these free maps.

Download Page : http://www.aversis.be/hdri/hdri-free.htm