Which disc brake pads do I need for Tektro Auriga? I have Tektro Auriga Sub disc brakes and the pads need replacing.

The only pads for this make I could find online were discontinued. Do I need to get the same make, and if not how do I know they'll fit?

Disc brake pads looks like a minefield. There are so many makes and types. Are there any general things you need to look out for.
Not an answer you want to hear, but Tektro parts are very sparse because they are entry level, and low budget. No one really makes parts for them other than tektro. So if its discontinued you may see if a bike shop can make something else fit, but online you will likely not find a match by visual.

Avid or hayes make brakes that are more universally supported.