We claim the ornamental design for the double-sprocket bicycle adapter, as shown and described.
FIG. 1 is a perspective view of a double-sprocket bicycle adapter showing the new design.
FIG. 2 is right side elevation view of a double-sprocket bicycle adapter showing the new design with the left side elevation view being a mirror-image thereof.
FIG. 3 is top plan view of a double-sprocket bicycle adapter showing the new design.
FIG. 4 is a front elevation view of a double-sprocket bicycle adapter showing the new design; and,
FIG. 5 is a bottom plan view of a double-sprocket bicycle adapter showing the new design.
The broken lines in the figures are intended only to aid in the understanding of the claimed design, are for illustration purposes only showing an article upon which the claimed design may be associated or applied, and form no part of the claimed design.