The ornamental design for a strap for a mobiledevice holster, as shown and described.
FIG. 1 is a top, rear perspective view of a strap for a mobile device holster;
FIG. 2 is a top, rear perspective view of the strap of FIG. 1 shown in use with a mobile device holster;
FIG. 3 is a rear elevation view of the strap of FIG. 1;
FIG. 4 is a front elevation view of the strap of FIG. 1;
FIG. 5 is a left elevational view of the strap of FIG. 1;
FIG. 6 is a right elevational view of the strap of FIG. 1;
FIG. 7 is a top plan view of the strap of FIG. 1;
FIG. 8 is a bottom plan view of the strap of FIG. 1; and,
FIG. 9 is an enlarged view, shown in region 9 of FIG. 3.
The broken lines showing a mobile device holster in FIG. 2 depicts environmental subject matter that forms no part of the claimed design, while the remaining broken lines shown in the drawings depict portions of the strap that form no part of the claimed design.