The ornamental design for a cover of a rehabilitationdevice, as shown and described.
FIG. 1 is a perspective view of a cover of a rehabilitation device showing my new design;
FIG. 2 is a front view thereof;
FIG. 3 is a rear view thereof;
FIG. 4 is a left side view thereof;
FIG. 5 is a right side view thereof;
FIG. 6 is a top plan view thereof;
FIG. 7 is a bottom plan view thereof; and,
FIG. 8 is a perspective view thereof shown in use.
The broken line showing the legs, and straps with the cover for a rehabilitation device in use illustrates the environment of the claimed design and forms no part thereof.