Suggestion: Look for the gma file on your garrysmod/addons folder and extract it via gmad.exe and put the extracted folder on the same addons folder.

Make sure your materials/models folder with the vmt/vtf files:
https://drive.google.com/file/d/11Wsuym3_hWwTMq3mvWEPJh6bksFLyazb/view?usp=sharing