Amazon is preparing its own mobile credit card reader that could go on sale next month at Staples,_9to5Mac reports, citing_internal Staples documents that it has obtained. The “Amazon Card Reader” is said to cost $9.99 and will probably connect to smartphones to carry out payments. The Staples documents show that the company has asked its stores to wait until August 12 to put up new signage related to the card reader. News of this card reader comes a few days after Amazon quietly released a_new Android and Fire Phone app, Amazon Wallet, that lets you store and organize your gift,...