With the loss of Nightrider's valuable OSM maps for SE Asia, I was looking around for a replacement. Earlier this month, I found it. OpenMapsChest.org uses the same OSM dataset that Nightrider used and it updates every week. The weekly updates include a .img file for the Garmin SD card and a gmap file for use with Basecamp. I've tried them on my Zumo XT, Zumo 396, and Basecamp on my iMac and all have worked just fine.
David
David