Looking for a battery... help?

[rawfuls]

Well, long story.
But I need a battery.

Well you knew that!

Looking for around $20

I need a single cell, (3.7V), roughly as much mAh as possible.
Size requirements is about 90mm (length), 55mm (height, well, if it's flat, and you're overhead). 5 or so mm width

OR

75mm length, 55mm height, 20 mm width.

It's fitting in an altoids tin if you're asking.

I can do 2S, but would like it to be fairly cheap (and the single cell to fit those specs).

Here's what I'm looking at so far..

http://www.amazon.com/Tenergy-Li-Ion.../dp/B001JE8U4Y

Thanks in advance guys, person who can find such a deal, gets a cookie!