I use a tool bag I bought at Lowes. It cost around $30.
Craftsman also makes some nice "tool" bags.
Check your local laws. NC is kind of easy going, as long
as the weapon is not "immediately accessable". I'd at least
keep the bag locked and in the trunk. A lot has to do with
the officer's first impression of you. I had an employee who
got a dui with a loaded shotgun behind the seat of his truck.
It was hunting season and he didn't get charged, with the weapon, at least
A friend's not very respectable looking son got pulled over one night
smoking whatever kids smoke these days. He had a realistic looking
pellet pistol under the back seat. He got a weapon charge as well
as being charged with whatever they were smoking. His father told me
the judge wasn't real amused and this one made an impression on the
young man.
The "tommygunner" violin case looks great. I want one. It might lead to
a serious misunderstanding if you happened to take it into a restaurant,
though, especially on St.Valentine's Day.