I quite like my lezyne super gps
to be clear though it doesn’t have maps stored on the device
it does have turn by turn directions and bread crumb trails which work well
rerouting needs the lezyne app running on a smartphone and a data connection
It’s easy to download tcx files from ridewithgps and then upload to the lezyne website which are then synced with the lezyne app
You do need to use the web version of ridewithgps though I think to extract the tcx file which isn’t great on a mobile. I just download routes on a pc to Dropbox then upload to the lezyne gps root website on a phone