How do I go about finding the right filter and oil for my Gen 2 Prius?

Aftermarket Gen2 Oil Filter Part Numbers: STP S4967, Fram PH4967, Purolater L14476, Fram 4967,AC Delco PF1233, & Bosch 3311.*

*- according to clerk at Autozone.

Toyota Gen2 Oil Filter Part Number: 90915-YZZF2

 

Or just use a Toyota dealership with online parts sales, say McGeorge Toyota parts.

 

Um......
OK.

First thing's first.....how much did that 'free'oil change cost you?
The belt goes for about $10 and it takes about 20 minutes (for me) to replace.
A mechanic can do it in under 5.

Don't mean to make you feel bad, but if you ever forget what kind of oil to put in your car, open the hood and look on top of the engine. Your oil filler cap might look like THIS:

It does not matter what KIND of oil you get as long as it has the API "starburst" symbol and meets the standard for energy conserving (they mostly ALL do) but MOST IMPORTANTLY you need to have the right quantity of oil in your engine!
And....in your case it should be 5w30........for now.
@ydpplqbd very helpfully provided you with some filter options.
The YouTubes will show you how and perhaps what tools you need.

Learn About Motor Oil Standards : Motor Oil Matters: Motor Oil Matters

Check your oil level as soon as you read this, and then every other time you fill up the tank.
Consider NOT going to the dealership when you need brakes.
Consider watching some YouTube videos for all of the common fluid and filter checks for your car and maybe spend $100 on some tools instead of another oil change.

Good Luck!

 

DIY is definitely cheaper than getting doinked over by the dealer, although to be honest I'd probably pay an independent mechanic to do the rears on the G2.
I hear a lot of comments about cleaning and lubing the slider pins on the G2, so pay particular attention to that. I Haven't done brakes on this car myself so I can only relate what I've read over the years.

Good Luck!!

 

Repair Manual info:

 

I could be wrong, but isn't there just one belt?