I've got a couple of 5 gallon diesel cans that I NO longer carry. Like some of you I thought I might run into a problem finding diesel. Carried the cans for about a year. NEVER had to use them. Contrary to some information out there states west of the Mississippi do have gas and diesel plus many of the other items found in more "civilized" parts of the country.
If you have a 29 gallon tank you'll be looking for a place to "rest" long before you need fuel. I wouldn't worry about finding a station to service your diesel needs. If nothing else follow the 18 wheelers! They'll lead you right to a station.
As far as the legal aspects..... I'm not aware of any states that prohibit carrying diesel cans. I suspect that since it is not nearly as volatile as gasoline it would not have the same type of restrictions. Please let us know if you come across any info that spells out any state restrictions.
Good luck and enjoy!
HamRad