FIG. 1 is a perspective view of a handheld shower showing our new design; FIG. 2 is a front elevational view thereof; FIG. 3 is a top end view thereof; FIG. 4 is a bottom end view thereof; FIG. 5 is a left side view thereof; and, FIG. 6 is a right side view thereof. The broken line showing is included for the purpose of illustrating and forms no part of the claimed design.