Designed in Fusion 360, I uploaded the .step files so that you can make your mods

Use a MK8 Extruder Gear, 608zz bearing (fidget spinner, longboard/skateboard bearing), a M4 nut, and the stock spring that came with the tevo tarantula

Simply put this on the outside of the motor mount with the motor on the inside, update your esteps in firmware and done! Just make sure your PTFE looks like it does in CAD, cut correctly and such.