The trash bag is a new item from The Escape team dlc.
It does not have to be crafted, and is found in cabinets. They are common (usually always in your own room) or sometimes in the rooms at the top.
Once you have one, select Shaun using
, press
to go to the give menu. Put the trash bag in, press
to confirm and your achievement will pop.
This will give a big reputation boost for Sean.