You can buy $100 Staples gift codes for $85 at Paypal Digital Gifts via eBay.
You can save more money by registering for eBay bucks to get 2% cash back extra on everything you buy on eBay. You may also want to check your email if you have been targeted for a 4X (8% back) promotion.
The deal gets even better if you use your Chase Ink card to earn 5 points per dollar eBay purchases. And if you go through Befrugal or Topcashback you can get an additional 1.5% back.
There is a limit of 5 Paypal Digital Gifts per buyer.
Keep in mind that e-Gift Cards are a bit harder to get rid off than physical cards, but with so many options for points and cash back, it should be worthwhile.