These Hamamatsu UV-Spot Light Sources can be found on spin coat tracks such as the Dainippon Screen DNS-80, DNS-60, SK200 and others. GetSpares.com, LLC has them in stock fully tested and ready.
The part number for the whole exposure assembly is L6001/L6299. One of the common failure modes is when the UV light will not ignite or has a weak output. The obvious culprits are the 50Volt igniter and the lamp part number L6190 / DNS 2-39-51072. Assuming that those are known to be good, the next common failure is with the AG09 50V power supply. These power supplies units can easily be swapped out with 8 screws in less than 10 minutes.