Yes that Talentcell battery specs 20000mAh at 5V so it should run the DR40 over the USB for quite a while.
Heads up on the Photek stand - the top stud is 1/4 inch thread and is NOT removable or reversible like other stands so you will need to adapt the thread size to 3/8 or 5/8 depending on your mounting hardware. I usually clamp my stereo bar onto it with a Windtech C clamp.