Use Your Companion
As long as you’ve chosen not to wander the wasteland alone, you’ve always got a sneaky way of keeping extra items nearby that your character cannot physically carry. Simply talk to your chosen companion and ask to trade. Throw in any extra pieces of equipment that you can’t carry, but you want to keep hold of. The best practice for this is to give them items that they cannot possibly use. You don’t want to hand them that hefty Missile Launcher only for them to use it in a confined area of combat and take your arm off.
Companions seem to have an unlimited carry capacity too, meaning you could quite literally use them as a storage box for any junk and apparel that your carry capacity won’t allow you to have directly to hand. Our chosen pack mule is Dogmeat, because even if you give him weapons, he can’t use them. Just make sure you don’t lose him in the wasteland if he’s carrying your Fatman!