We'll cut to the chase on this one - head over to Samsung's US mobile accessory site here, and use the coupon code 'rE155266e' when you reach the checkout page. That code will give you 50% off of all Samsung Mobile US accessories.
So, for well under $100 shipped (free UPS ground on orders over $50), you can a spare Note II battery, S-Pen, and a Samsung AllShare Cast Hub (normally $100 by itself). Or, for under $100, you can get two batteries, an S-Pen, and a case. Now that's a deal.
We don't expect this coupon code to last long (let's face it, we doubt Samsung can afford to sell Note II batteries at $25 a pop), so get on it while it's there!