As a result of our work with lanthanide imaging, I’ve acquired an interest in excitation sources in the deep UV (DUV; around 280 nm). When we started a few years ago, the only options were arc lamps. Now there are a number of companies that produce DUV LEDs with decent emission powers. I haven’t yet tried any of these, though I plan to soon; I’m posting this list in case someone else is looking for suppliers.
Thorlabs makes a mounted LED that provides 25 mW at 280 nm. Other suppliers of component LEDs (i.e. you supply the power source and mounting) are: