We claim the ornamental design for a syringe holder, as shown and described.
FIG. 1 is a side perspective view of our new design for a syringe holder, shown in use;
FIG. 2 is a bottom perspective view of the syringe holder of FIG. 1;
FIG. 3 is a side view of the syringe holder of FIG. 1;
FIG. 4 is a front view of the syringe holder of FIG. 1;
FIG. 5 is a rear view of the syringe holder of FIG. 1;
FIG. 6 is a bottom view of the syringe holder of FIG. 1; and,
FIG. 7 is a top view of the syringe holder of FIG. 1.
Broken lines are used to illustrate portions of the syringe holder other broken lines illustrate environmental subject matter neither form no part of the claimed design.