The ornamental design for a portable fireplace, substantially as shown and described.
FIG. 1 is a front perspective view of a fire cradle for a portable fireplace shown separately for ease of illustration in my new design;
FIG. 2 is a rear perspective view of the portable fireplace;
FIG. 3 is a front perspective view of the portable fireplace;
FIG. 4 is a front elevational view of the portable fireplace;
FIG. 5 is a rear elevational view of the portable fireplace;
FIG. 6 is a right side elevational view the of the portable fireplace, the left side is a mirror image;
FIG. 7 is a top plan view of the portable fireplace; and,
FIG. 8 is a bottom plan view of the portable fireplace.
The broken lines showing the openings in the fire cradle, a rear vent, the overlapping mounting strips of the roof and side panels, and the interlocking screws and keyhole mounting slots are for illustrative purposes only and form no part of the claimed design.