I've been scouring the internet for a site where I may order a custom shaped mirror that reflects UVC light. The most I could find is that polished aluminum and magnesium oxide will reflect UVC light but it was simply something said in a forum.

Does anyone know if such a mirror exists and where to find a company who makes it?

You are not being precise.

Do you mean:

a] 280 nm - 200 nm
or
b] 280 nm - 100 nm?

Aluminum does stay shiny (more than 90% through both ranges, but below 200 nm, the oxygen in the air will absorb the UV. If a is not enough, you need to work in vacuum or a pure nitrogen atmosphere.

I have never heard of someone polishing magnesium oxide -- it usually used as a diffuse reflector, not a imaging, polished mirror.

Do you need a rough focus or optical quality? For an optical quality focus, the mirror must be polished to a specification of 1/4 of the relevant smallest wavelength. This will add to the cost.

Finally, since every university library has these answers in the CRC Handbook of Chemistry and Physics, you probably are working without adequate instruction and supervision and may seriously injure yourself by pursuing this project without experienced guidance, which I am not. Why you would consider Internet advice on a project this dangerous to your health is beyond me.

~253.7nm seems to be the most common given off by germicidal lamps.
I first thought of using Fabry-Perot interferometers, lining the inside of the globe but decided that it would be unnecessary to use something so elaborate.
Also searching for a company who can do it was fruitless. My guess is that the expense would be very high as well.

QUOTE

Do you mean: a] 280 nm - 200 nm or b] 280 nm - 100 nm?