The ornamental design for a rotatablebase accessory for a fitness balance device, as shown and described.
FIG. 1 is a top perspective view of an ornamental design for a rotatable base accessory for a fitness balance device;
FIG. 2 is a top perspective view thereof, showing a fitness balance device positioned on a top plate of the rotatable base accessory;
FIG. 3 is an exploded left side elevation view thereof;
FIG. 4 is an assembled left side elevation view thereof;
FIG. 5 is an exploded top perspective view thereof;
FIG. 6 is an exploded bottom perspective view thereof;
FIG. 7 is an assembled bottom perspective view thereof;
FIG. 8 is a top plan view thereof; and,
FIG. 9 is a bottom view thereof.
The broken line showing of the fitness balance device in FIG. 2 is for the purpose of illustrating environment and forms no part of the claimed design.