Here you have one of them. It fits just exact on height 4.8 cm, and is a little small on width so it fits fine on the hole of the walkera Devo 7 transmitter. You need to cut the transparent plastic to use the touch capabilities. There are other screens of 2.8'' but all of them have 5.0 cm of height and don't fit in the hole of the transmitter. This is the only one with 4,8 cm and a big colour touch screen. It has a connector that can be soldered, and without PCB to have more space and be capable to be at place without to retire the lateral buttons of the transmitter.
I have not readed the datasheet but it seems to work with a parallel interface of 16 bits, I think should be better with 8 bits to use less GPIOs on the microcontroller, and it works with 2.8 Volts.
Here you have some of 2.8''. They fit fine on the width but they measure 5,0 cm on height and don't fit on the hole, you need to cut the transmitter case to fit them.