A craftable post bag for you to equip, simple as that.
You can craft it at the chem station in the bags category and you need some leather and adhesive.
It raises your endurance by 1 and more importantly your carry weight by 30 for you or your companion.
Downside is that it uses the chest slot for armor pieces. But fear not because it hides your butt so you get a 1 DR bonus, too.
Update v1.1
Added armor crafting station support
-It is now possible to modify the Post Bag with two addons which raise the carry capacity by 10 / 20 lb.
-The larger upgrade also requires Armorer Perk 1.
Installation:
Make sure your game is mod ready.
It uses TEXTURES, MESHES and MATERIALS.
NMM compatible.
Created with FO4Edit, Material Editor, and Nifskope.
Big thanks to those people.
Sidenote: Some clipping issues with larger armor.
Authors:Lex
