http://www.gainesbasswheel.com/
An excellent bass wheel, albeit an expensive one. It is quite durable on any surface...gravel, city side walks, deep forest trails, and perhaps a mud bog or two.
It takes a bit of getting used to when wheeling around a bass, but it is a lifesaver, especially in situations like yours (carrying long distances vs. a wheel). Uncomfortableness occurs on occasion, but nothing big.
Summed up: go with a wheel.
Alex