I would recommend either Emperor or Aqua UV. There are others that may work, although do not have the reputation these do.
My experience with UV over the years is that most work, and 'some' are poorly designed/made.
There always seems to be very strong, even extreme, opinions on this topic as to which units work, are 'best', etc. This might be one of the few true facts you find when researching UV sterilizers
I believe that such strong opinions are bred in part by the fact that these units are so expensive to purchase. Everyone wants to think that they bought 'the best', and no one wants to think they made a bad purchasing decision.
UV technology has been around a very long time. I have not seen a quantum increase in effectiveness nor reliability, since buying my first one almost 30 years ago. I still own it and it still works, and is all original, except for the bulb. In fact, the company isn't even still in business. Such reliability may be partly to blame for the company failing.
You might consider buying one used, though inheriting someone else's headache (or junk) is always a possibility.
Rule of the day:
Caveat emptor (buyer beware)
Also:
Bio balls are not inherently a bad thing. The problem is what to do with the nitrate byproduct. Using a denitrator in tandem will yield a 'complete' solution to handling nutrients.
The healthiest system I ever had used both. Most hobbyists are just not familiar enough with these systems to get such results, so they avoid them, IMO.
My $0.02
