The ornamental design for the foldable beach or lawn chair, as shown and described.
FIG. 1 is a front perspective view of the foldable beach or lawn chair in accordance with my new design;
FIG. 2 is a rear perspective view of the foldable beach or lawn chair in accordance with my new design;
FIG. 3 is a front elevation view thereof;
FIG. 4 is a rear elevation view thereof;
FIG. 5 is a left side elevation view thereof;
FIG. 6 is a right side elevation view thereof;
FIG. 7 is a top plan view thereof; and,
FIG. 8 is a bottom plan view thereof.
The broken lines shown in the drawings are for the purpose of illustrating portions of the foldable beach or lawn chair and form no part of the claimed design.