The ornamental design for a sialendoscope, as shown and described.
FIG. 1 is a bottom left side isometric view of a sialendoscope in accordance with the new design;
FIG. 2 is a left side elevational view thereof, the right side being a mirror image;
FIG. 3 is a top right side elevational view thereof, the top left side being a mirror image;
FIG. 4 is a top plan view thereof;
FIG. 5 is a bottom plan view thereof;
FIG. 6 is a rear elevational view thereof;
FIG. 7 is a front elevational view thereof;
FIG. 8 is an enlarged partial view of FIG. 6;
FIG. 9 is an enlarged partial view of FIG. 7; and,
FIG. 10 is a bottom left side isometric view of the sialendoscope of FIG. 1.
FIGS. 1-5 show a break indicating two parts of the sialendoscope for ease of illustration. The portions of the sialendoscope shown in broken lines in FIGS. 6-9 depict environmental subject matter and form no part of the claimed design.