I absolutely second this request. For a cult favourite, it's surprising that we haven't gotten maps for this yet.
I should mention the
Mother 3 Handbook available from Fangamer.com. This is not a sponsored post, I just thought it was cool to point out. It's a fan-made guide, that, like some of the reviews say, is also a work of art. 272 full-colour pages featuring illustrations and sculpted models, it perfectly captures the essence of the EarthBound Player's Guide by Nintendo Power which was included with the Super NES game. The Mother 3 Handbook is in English and based on a translation patch for the GBA game, I'm sure. It is $32, and there is also a $6 digital version (.PDF).
Of course, I'd still like directly-ripped maps for VGMaps.com, so hopefully in sharing this I haven't reduced the likelihood of that...
EDIT: Wait, now I'm not sure if this actually has directly-ripped maps. The description doesn't claim to, but does say they have "custom-designed and hand-drawn maps, diagrams, and illustrations". They certainly don't make it clear in the photos. These two shots below seem to show maps but one is clearly not ripped and the other seems monochromatic. Unless the area is supposed to be that way, I don't remember, it's been a while. Does anyone have this book? Or should I dive in and get at least the $6 .PDF file to see for myself?