Haven't gone cruising yet, but I have backpacked and camped for weeks a time where fresh water was a luxury.
If your hair is oily, sprinkle a bit of cornstarch on your scalp, rub it into your scalp, then brush it out. This works to absorb oil between washings.
If your hair is dry, TiGi After Party is a great smoothing cream that removes odors and restores moisture. The packaging is a bit bulky and awkward, but a little goes a long way so one can should last you for a long time. It uses no propellants so that is a definite advantage.
When my hair was longer ( to my waist) I used the cornstarch on my scalp, then a small bit of After Party on my ends, braided it up and went about my business. Be sure you use the cornstarch first other wise it will stick to the After Party which will requre you to wash your hair immediately, which is what you were trying to avoid in the first place.