FIG. 1 is a top plan view of a heat pack foot warmer, showing my new design;

FIG. 2 is a right elevational view thereof, the left elevation being a mirror image thereof;

FIG. 3 is a front elevational view thereof;

FIG. 4 is an enlarged sectional view of a portion thereof as taken on line IV--IV of FIG. 1 to more clearly show the ornamental design thereof;

FIG. 5 is a bottom plan view thereof;

FIG. 6 is a rear elevational view thereof;

FIG. 7 is a reduced perspective view thereof shown mounted on a boot.

The broken line showing of a boot in FIG. 7 is for illustrative purposes only and forms no part of the claimed design.