http://pitviperstudios.net/ - Pit Viper Studios is one of the leading manufacturers of GI Joe related costume replicas. Produces a wide range of helmets and accessories for classic ARAH characters and a great resource for building many popular troopers. They can be found on Facebook and Instagram as well, just reach out to them for any inquiries.
https://www.facebook.com/The-Patch-Czars-Custom-Embroidered-Patches-146973142664771/ - Custom made patches. Need something unique made, Patch Czar is your man. He has a collection of many unique and rare emblems available for creating patches and embroidery.
https://www.facebook.com/XeroProps/?ref=br_rs - Custom 3D printing by a fellow Finest member. Has a library of GI Joe accessories already available to choose from and can create many unique items you wont find anywhere else.
https://www.etsy.com/shop/AlpineTraditions - Custom made 3D printing and other costume services.
Looking to build a Viper, then Alpine can help you with many of the important soft goods! Unique helmets also available such as Steel Brigade, Snake Eyes, and others along with all kinds of accessories. A vital resource for Iron Grenadier builds, reach out to Alpine Traditions to inquire about getting custom gear made for your costume build! Just sent them a message about anything you need.