Amazon offers its Prime members the CardNinja Ultra-Slim Self Adhesive Credit Card Wallet for Smartphones in Steel Gray for $7.95 with free shipping. (Non-members can spend $49 or more to qualify for free shipping; otherwise, shipping costs $6.03.) That's tied with our mention from a month ago and the lowest total price we could find now by $7. It's compatible with a range of iPhones and Android smartphones and holds up to eight cards and cash.