I had the same issue with my Pi 2 and tried all sorts of different chargers to no avail, same as you - I tried a powered hub for the screen, but lost sound when I did that. I tried the screen directly powered from the mains and again had the same problem.
In the end, I modified config.txt in /boot and added the following line at the bottom:
max_usb_current=1
I'd seen in mentioned in a few places as that boosting the amount of current that the USB socket will dish out. Whether it's likely to fry the Pi or the screen or anything, I don't know - but since I added that, my screen hasn't crashed.
