Great news.
I have just finished designing and printing a very cool charge adaptor for the track loader.
It will be available within the next couple of days.
The Charger can be found here: https://www.thingiverse.com/thing:2794970

I'm still working on this project. More files will come. More description will come.

This is my take on the Mini Track loader.
Instead of using an RC Remote I wanted something that would be more easy and lightweight to bring along with me on a daily basis.
So I redesigned the body to get more space inside for a Arduino Pro Mini, a Bluetooth module, a small 1s lipo battery, an on/off switch and a charging plug. Plus a little extra.

https://youtu.be/NIg1I9ntlLo

This Track loader is based on the files from @lijingwei
https://www.thingiverse.com/lijingwei/designs
Lijingwei writes:
"This is a bigger track load using 9gram servo .
All parts are all redrawn based on Zedpi’s Mini Track Loader RC.
The Lego track is no more supported ,You have to print track with flex material .
The servo I'm using is emax es08ma , other similar 9gram servo should be ok but not tested"

Parts needed:
1x Arduino Pro Mini https://goo.gl/D2z6b4
1x Bluetooth Module https://goo.gl/hRQhzv
3x SG9 servos https://goo.gl/fRvFBf
1x On/Off switch https://goo.gl/78AyvA
1x 1s Lipo 180mAh https://goo.gl/Hp6TaL
1x 2 pin SH size connectors https://goo.gl/r2ni9r

Optional:
1x FTDI USB Adaptor https://goo.gl/Tt3dWA
1x Mini buzzer 5v https://goo.gl/62NGMi
1x Yellow 5mm LED
PAD-11 Crimp Tool https://goo.gl/U5KtBk

UPDATE 2018.01.15
The android app used to control the track loader is made by Andi.Co and can be found on google play store.
https://play.google.com/store/apps/details?id=braulio.calle.bluetoothRCcontroller

UPDATE 2018.01.17
The Arduino code is now uploaded.
It's a very modified version of the one Andi.Co has made.

UPDATE 2018.01.21
Schematic is done. Added here as a picture and in the Post-Printing section.

UPDATE 2018.01.22
Added description for modifying the belt servos in the Post-Printing section.

UPDATE 2018.02.09
Updated files section. I had made some fuckup in the wheels and track files.
Now you will have 2 options: Big track or Lego track. 4 files for each and they should be clearly marked.