If you have TF2 on Steam: You could copy the GCFs over to Gmod's folders. If you know a bit of scripting you could convert them to addon format.
You can find all the content on Gmod.org though, but that actually requires that you own Gmod on steam if you wish to download anything. I don't think I can post a link, since it might be considered "Warez", and I don't own Gmod on my current Steam account so I can't DL them myself and send you the files.
Try experimenting with some Draging/Droping of a few models, and you might pioneer a solution.