I've now uploaded the newer version on Thingiverse as well: https://www.thingiverse.com/thing:2970246
Since it has come up in the comments I'm going to use that as an excuse to shamelessly promote my grip for the Original 3DS Xl
New version is now available: http://cults3d.com/en/game/ergonomic-grip-for-3ds-v2-original-3ds. This version will remain available for free on Thingiverse but if you'd like to support my endeavours then consider buying the new version.
As an aside; whilst I don't have any personal interest in altering the grip for other versions of the 3DS/DS, it's not out of the question if there's enough interest, so do let me know.
With some minor sanding this grip will fit a DS Lite.
Yet another ergonomic grip for the least popular iteration of a handheld... I'm really quite happy with this one, it's much simpler and more elegant than the one I made for Vita. No retention peace or anything like that, just plain old friction to hold it in place. The only thing covered-up is the SD-slot but that really shouldn't bother anyone.
I used superglue to put the peaces together and some adhesive pads for a bit of extra friction. I highly recommend water sanding with (at least) grits 120 and 240.
10% Zig Zag, 1 step granular infill (bottom peace)
Printing with PLA, 3 shells (1.2mm) seems appropriate, resulting in a strong print with plenty of margin for post-process sanding.
I like printing these sorts of shapes with concentric top bottom patterns, although be forewarned that the flat (roof) bit on the bottom peace requires quite a bit of infill for concentric to turn out well and the more top layers the better.