Purchasing my first UV Sterilizer

After a nasty bout with septicemia, and the fact that I'm leaving the
country for two months so the care of my 30 gallon tank will be left to
someone else (responsible, but not that into goldfish) I'm
contemplating a UV Sterilizer for my tank. It's got 2 goldfish in it.

I currently have an Aquaclear 50 HOB filter. It's my understanding that
with a UV sterilizer, you need either a canister filter or a powerhead
to draw water through it.

I'm assuming the UV Sterilizer is going to cost $100, and a canister
filter would cost $100. Powerheads look like they run a variety of
prices, from $5 and way on up. I've never even seen a powerhead before,
so I really don't know what I should be looking for in one. Or what I
would need to attatch it to the UV Sterilizer

Since I'm worried about bad bacteria lingering in the filter media,
having a UV sterilizer attatched to a canister filter seems like a good
idea. But I'm not sure if this is a realistic worry, and canister
filters are really expensive. What's the cheapest canister I can get
that would be good for this purpose? Or should I just go with a
powerhead since I already have a filter?

Thanks in advance,
Kelly