For a mineral solution (and assuming you have access to some polishing gear...) fluorite from the Weardale valley in England is about the most fluorescent stuff there is. Some will actually fluoresce visibly in daylight. The Rogerly mine is famous for coke-bottle green glassy clear cubes up to 1/2" or more. If you could grind down and polish a piece of that you might have some luck. It is particularly sensitive to LW UV (around 350-370 nm). eBay often has samples for sale in the Fluorescent Mineral section and the Yahoo Group for fluorescent minerals may have a dealer/collector who could supply suitable material.
Cheers.
-------------------- Steve
16" Meade LightBridge (Beowulf)
10" Hardin DSH, StarMax 127mm Mak, PST H-a
Oberwerk 11 x 70 binocs, Tasco 10 x 50 binocs