Are you sure that you really need a new battery? A three year old battery that has never been run flat should still be in pretty good condition. If it does need replacement, I would get the least expensive battery you can find that has the same or slightly better specs than the original. With your style of camping, you just don't put enough demand on a battery to justify spending any more than necessary.
Gary and Pat Harkins
Dodge 3500, 2011 CF305SKP