I have used a light tent. There is then the problem of losing the scintillation of light from a gemstone. A nice light source is needed to shine into the gem to reflect back and make the stone come "alive".  Light tents work fine for reducing metal glare but unfortuntely reduce the lively aspects of a transparent gemstone, too.

The fibers from the fiber optic lamp will work..now just to get a source of white light to feed the fibers!

The IT shop might be good bet..but to get a light and fibers together would be easier..albiet likely much more costly.   

Good ideas...I will check these out.   Tom.