Never done this before but based on plants I have shipped in the past .....

Make sure the moss is only barely damp to minimize molds having a field day while it is in transit.

I assume you intend to pack the bubble wrap INSIDE the jar?
I would try to have a sheet of the bubble wrap cut to lay atop the moss "ground" like a blanket. Then stuff the jar with either bubble wrap or, if you have any on hand, those plastic inflated shipping bags.

Definitely tape the lid down and don't skimp on the packing material you surround the jar with inside whatever box you use for shipping.