I picked up the unbranded 5" WinCE device from eBay.
To install, see
SkyDemon Mobile, GPS handheld navigation devices for aircraft on which there is a linked forum with suggested devices and tips.
SkyDemon on Third-Party WinCE Devices
Device feature comparison here:
Compare SkyDemon Versions
If you have the desktop software, there is a simulation mode which shows you what you get (and what you don't) when using the WinCE version.
Considering the price of Android devices these days - if you are going to buy something then I'd go down that route for the extra functionality.