The obvious answer!
THE ORIGINAL HELIUM-FILLED LUMINOUS ARTIFICIAL SUN:
http://www.elfis.net/elfol7/e7artsun.htm
Excerpt:
"Floating as high as 50 feet in the air, turning night into day, this 2600-watt artificial sun will illuminate a 15,000 to 20,000 square-foot area with soft, ambient lighting. "
Best,
Kurt