[Cyclopswc]

I like Thingiverse and Cults3D.

https://www.thingiverse.com/

https://cults3d.com/

And best of all, most things there are FREE. Cults does give you an option to buy. There are a LOT of stuff for GIJoe Classified made already, I 3D printed a Chameleon for Zartan and some guns.



As for scaling, that's just math. Most models the description would tell you what scale it is. Just search "G.I.Joe" you'll find a LOT of stuff. However, say if you found something was done for the 3 3/4" Joes, you simply print that thing at 150% and that'll get your 1/18 item to 1/12. Just mindful that not everyone does their stuff exactly to scale, so sometimes you do have to fidget it a bit.

Have fun!!