I claim the ornamental design for a tracheostomy cover plate, as shown and described.
FIG. 1 is a front elevational view of a tracheostomy cover plate showing my new design;
FIG. 2 is a rear elevation view thereof;
FIG. 3 is a left side elevational view thereof;
FIG. 4 is a top plan view thereof;
FIG. 5 is a bottom plan view thereof; and,
FIG. 6 is a front, left perspective view thereof.
The broken line showing of the straps illustrates the environment of the claimed design and forms no part thereof. All other broken lines illustrate portions of the tracheostomy cover plate which form no part of the claimed design.