Where to obtain sprites

I've searched endlessly but have never been able to find sprites that quite do the job.

Depends on what your looking for.
Like a sprite that already exists in games or a custom sprite of something.
You need to be a little more specific about what your looking for and or who?

2D sprites to use in side-scrolling videos and/or comics.
The most important thing to me is Link, whether it's Zelda II Link or a custom Link, I want sprites of Link that faces left and right. And maybe a Princess Zelda, and Dark Link?

Spriter's Resource of the Shy Guy Kingdom might have something, I believe. you might want to give credit if you use them, though...

The Spriter's Resource is the biggest sprite site, but that isn't to say it's the only. Some of the bigger ones are linked to in TSR's Resources page.

For Link and Zelda, here's their Zelda Customs & Edits page, it'll likely have the sprites you need:
The Spriters Resource | Custom / Edited > Z > Zelda Series

I actually have a custom Link, Gdorf,and Zelda all in a side scroll style.
all thanks to GoldStud!