The ornamental design for a housing for a mixerbase, as shown and described.
FIG. 1 is a top, front and right side perspective view of the housing for a mixer base, embodying our new design;
FIG. 2 is a top plan view thereof;
FIG. 3 is a bottom plan view thereof;
FIG. 4 is a left side elevation view thereof;
FIG. 5 is a front elevation view thereof;
FIG. 6 is a right side elevation view thereof; and,
FIG. 7 is a rear elevation view thereof.
The broken lines shown in the figures are for the purpose of illustrating portions of the housing for a mixer base and form no part of the claimed design.