We use these at our office: http://www.sitonit.net/home/product-overview.asp?product=focus http://www.sitonit.net/home/product-overview.asp?product=foc... The

We use these at our office: http://www.sitonit.net/home/product-overview.asp?product=focus http://www.sitonit.net/home/product-overview.asp?product=foc... They are not as good as aerons but they are significantly cheaper, around $250.