Is it because you are afraid of accidentally striking hit several times with an hammer while transporting it?
Lipo Battery fire. - YouTube
Now, on a more serious note, I guess you could find a small metal can in a camping/hunting store that would protect your battery. Or maybe an empty coffee can would do.
Personally I've been carrying my Lipos in a regular bag for years without issue.
EDIT: Actualy, the only issue I had was the small charging wire ripping at its base making it impossible to charge my battery, so I had to buy a new one.