This repository contains a Mujoco model of Spot, created with MJCF modeling language.
I found .stl and .dae files, along with a spot.urdf.xacro file in this repository :
https://github.com/SoftServeSAG/spot_simulation/tree/spot_robomaker
I converted the .dae files to .obj format via Blender, I used obj2mjcf command like recommended in the Anymal C documentation of the Mujoco Menagerie.
I've coded the spot.xml file, structured based on the Anymal C XML, while using parameters from the spot.urdf.xacro file.