They do one the size of the empeg display, I believe with greyscale support too (it's a newer module - greyscaling was built into the drivers a year or so ago). Not sure on the part number, it should be on their site.

As for greyscaling on the small display; the small display is very bright because it's not a multiplexed display - it's a phosphor on silicon display. Instead of scanning, a lit pixel is lit continuously. It'd be possible to do greyscales by driving the glass directly, but it'd probably be non-trivial as a task.

Hugo