Containers in backpacks

Yes, there is, however, you'll need someone to piece a mod together for you to do that or add some lines to an existing one.
You can join the Discord and personally direct message me (DeadlyFirex#0117) and we'll get it done if you're interested

I am pretty sure there is an option for this somewhere already, so probably AIO.

This is not the place for this sort of discussion though, Discord is your best bet.