B&H has the SanDisk Extreme Plus 64GB microSDXC U3 card for $39.99 (reg. $55.99) through June 23. The U3 means it offers a minimum write speed of 30MB/s and it features a max read/write speed of 95/90MB/s. Check it out here at B&H Photo.
Learn more about SD card specifications and features in my article, Demystifying SD Cards.