The ornamental design for the balancer weight tray, as shown and described.
FIG. 1 is a top-right perspective view of the balancer weight tray;
FIG. 2 is a top-left perspective view of the balancer weight tray of FIG. 1;
FIG. 3 is a top plan view of the balancer weight tray of FIG. 1;
FIG. 4 is a bottom plan view of the balancer weight tray of FIG. 1;
FIG. 5 is front plan view of the balancer weight tray of FIG. 1;
FIG. 6 is rear plan view of the balancer weight tray of FIG. 1;
FIG. 7 is a right side plan view of the balancer weight tray of FIG. 1;
FIG. 8 is a left side plane view of the balancer weight tray of FIG. 1; and,
FIG. 9 is a top-right perspective view of the balancer weight tray of FIG. 1 installed for context on a wheel balancer structure, the wheel balancer structure forming no part of the claimed design.