The ornamental design for a space-saving travel bottle, substantially as shown and described.
FIG. 1 is a front perspective view of a space-saving travel bottle showing our new design;
FIG. 2 is a front view thereof;
FIG. 3 is a back view thereof;
FIG. 4 is a right side view thereof;
FIG. 5 s a left side view thereof;
FIG. 6 is a top view thereof; and,
FIG. 7 is a bottom view thereof.
The broke line showing portions of the space-saving travel bottle is included for the purpose of illustrating environmental structure and forms no part of the claimed design.