The ornamental design for a towelholder for loungechairs, as shown and described.
FIG. 1 is a top view of a towel holder for a lounge chairs showing my new design;
FIG. 2 is a right side view thereof, the left side view being a mirror image thereof;
FIG. 3 is a bottom view thereof;
FIG. 4 is a front view thereof;
FIG. 5 is a back view thereof;
FIG. 6 is a front side isometric view thereof;
FIG. 7 is a back side isometric view thereof; and,
FIG. 8 is an isometric view thereof in use with a towel and lounge chair.
The broken line showing of a lounge chair, feet in FIG. 3 and interior features of a holder illustrates environment only and forms no part of the claimed design.