Hi TG

There are hundreds, all free... google for "HDR probe"
http://www.hdrimaps.com/
http://gl.ict.usc.edu/Data/HighResProbes/
http://www.debevec.org/Probes/
http://www.cgmill.com/olmirad/hdr.html
http://www.iseetheskyinyoureyes.com/

Try this polish site first, it has several probes from other sites:
http://www.max3d.pl/show.php?id=hdri

You may need to convert them to a format Poser understands, you can use HDRshop for that.

regards
pk
www.planit3d.com