If you have a working one which puts out nice filtered AC then you can just use it for your equipment.
I wonder
We've got server UPS lying around at work. Would UPS's smooth out power surges and the like?
This is actually their primary function. Keeping the device on for an extra couple of minutes is almost secondary in my opinion.
It depends on the UPS. Cheaper UPS products don't actually filter the mains AC, rather monitor it and step in when there is a problem.