Where to purchase an NES?

I've been doing well with my thrifting rounds in the last few days. I have nothing better to do as I'm away on vacation at my grandmother's house and hitting up stores is a pretty easy way to pass time.

As I'm about to go back home, though, I have a question. I love the idea of collecting games and shelving them and making them look all nice and pretty, but the urge to play them is way too much to handle.

I've discovered (so far, at least) that consoles come and go in these stores fairly quickly. That being said, what's the best place to pick these up OUTSIDE of looking for a ridiculously inexpensive lucky finds at Goodwill? Presently looking into Amazon, but buying used items from third-party sellers seems sketchy to me.

Any ideas, guys?