Waveshare is offering a wide range of E Ink displays for Raspberry Pi, and the company has now added 7.5" display option. The 7.5" E Ink display offers a resolution of 640x384, and can support either 2 colors (black/white) or 3 colors (black/white/red). The display costs $65 for the black and white version and $77 for the 3 color one.
Waveshare is now offering E Ink Raspberry Pi displays ranging from 1.54" to 7.5" in size. All of these displays are available on Amazon.com.