Rather boss'
Would "Do you have your boss' signature?" be a reasonable interpretation? For instance when talking about "grandma" the "my" or "your" is implied (jestem u babci), does it also happen with "boss"?
True, that makes a lot of sense here. Added now.
Please, accept version with boss'
It's already accepted.
And would be grateful too if you add to Polish speaking exercises
Sorry, but we can't add new features. Only technical staff can.