Veteran documentary DOP Bill Kerrigan needed to lighten his load when working with a single assistant, so he invented an equipment cart that doubles as a dolly / slider.
Matthews Studio Equipment is putting it into production, and they're working on a final version. From Matthew's booth at NAB 2015, Kerrigan explains how the KerriKart works. It breaks down so it will fit in his minivan and lets him do more shots in a day.
Price isn't final but it can be built up with standard Matthews grip gear to suit your needs.