I built a a very compact, battery battery-powered shortwave UV (254 nm) for about $30.
I used a hiker’s battery-powered water sterilizer and a piece of ZWB3 filter glass
and just built them into an old plastic bottle.
You can easily build an SW UV (254 nm) unit. At the end of the day, they are all just a UV source, a filter (to eliminate the extraneous blue light produced) and a “box” to contain everything, ALTHOUGH I RECOMMEND ADDING A BARE ALUMINUM REFLECTOR (ANY PAINT OR COATING WILL JUST ABSORB SW UV, DEFEATING THE WHOLE PURPOSE OF THE REFLECTOR) : YOU CAN ALMOST DOUBLE THE USABLE OUTPUT WITH JUST THIS SIMPLE ADDITION.
The ZWB3 filter glass will be you most expensive part, and it will absorb about 50% of the output of a typical mercury-vapor 254 nm source, but it absorbs almost all of the contaminating visible light emitted, and makes the lamp much more useful
If you like to build things, this can be a CHEAP way to go.