B&H Photo Video offers the Samsung Duo 64GB microUSB / USB 3.0 Flash Drive, model no. MUF-64CB/AM, for $19.99 with free shipping. (Amazon and Adorama have it for the same price.) That's $2 under our mention from last month and the lowest total price we've seen. (It's also a current best by $8.) This drive has both microUSB and USB 3.0 plugs and features transfer speeds of up to 130MB/s.
Of note, this item is currently on backorder at Adorama, but can still be ordered at this price for delivery when available.