Okay, after making some additional revisions for better friction-fit on the brackets, here’s the final STL files for anyone out there with a 3D printer!
The Thingiverse post has a complete BOM, so hopefully this winds up helping others who want a good portable battery solution.
I got rid of my crummy PVC tube and replaced it with a 3D printed one, which turned out to be a much nicer option. I uploaded the tube I printed as an STL as well, so the only off-the-shelf materials required will be a compatible phone charger and a USB to 5.5x2.1 power cable.
So far I’m really loving it - the dual purpose “stand” functionality is more useful than I thought it would be. I’ll almost certainly still buy the Elektron version when it comes out since it’ll be a much more polished product, but in the interm this works great!