Rigging - Sword like object influenced by 2 bones As in topic. How to attach a sword to have it be influenced by two bones. Not off course in the same time. 
I was fighting with "child-of" constraint, but with no luck. Well it works, but if I was in need to change bone influence form pelvis to left hand, it just fly away somewhere, so the transition wasn't seamless as I was expecting. I really don't have any idea on how to do this. I was experimenting a lot. 

Basically Sword bone must follow pelvis bone, when it's not used, and need to follow hand bone, when the animation need it. Anyone, because it's driving Me crazy. It can even be via payed addon, anything. 

Regards! :)
If there's only to be one parent switch, the Child of Constraint should do that, but for multiple switches or just plain simplicity, I'd be looking at (as you mentioned) visually switching between two swords, or even easier - splitting the project up between two or more Blend files, each taking over from the previous and each with the correct parent assigned. (Ctrl+P)
The transition would be simple enough.  As the hand would firstly have to move to the sword's handle you'd need to animate that in the 1st file with the pelvis as the parent.  Once the sword handle is gripped, that would be where the next Blend file takes over and with that running, the hand is the parent.
A similar case is here:
How can I copy animation from an object while it was attached as a child and then paste that animation to it after detaching it?