The ornamental design for a frame for a scooter, as shown and described.
FIG. 1 is a perspective from the front and side of an embodiment of the scooter;
FIG. 2 is a front perspective view of the scooter in FIG. 1;
FIG. 3 is a back perspective view of the scooter in FIG. 1
FIG. 4 is a right side perspective view of the scooter in FIG. 1; and,
FIG. 5 is a left side perspective view of the scooter in FIG. 1.
Features of the article that are not shown are not claimed. The broken lines shown are included for the purpose of illustrating portions of the scooter which form no part of the claimed design.