I haven't used UV myself, but have examined the relative role of blue, green, yellow, and red PAR wavelengths (using LED's) on seaweed communities.
UV LEDs are available in a range of shapes and sizes either as just the chip, or integrated into a working unit. Many underwater photographers regularly us UV LEDs for fluorescent techniques.
Depending on what you plan on testing, intensity and exact spectral range will be critical. A custom option may help you better suit your exact application.