We claim, the ornamental design for a syringe holder, as shown and described.
FIG. 1 is a front elevational view of a syringe holder.
FIG. 2 is a rear elevational view thereof.
FIG. 3 is a top plan view thereof.
FIG. 4 is a bottom plan view thereof.
FIG. 5 is a right side elevational view thereof.
FIG. 6 is a left side elevational view thereof.
FIG. 7 is a perspective view thereof.
FIG. 8 is a right side elevational view of the syringe holder shown in a position of use; and,
FIG. 9 is a right side elevational view of the syringe holder shown in a position of use.
The broken lines depict portions of the syringe holder, the sampling arm, and the sample receiving assembly that form no part of the claimed design; the broken lines and the unshaded surfaces form no part of the claimed design.