The ornamental design for a strap connection device for bags, as shown and described.
FIG. 1 is a perspective view of a strap connection device for bags, showing my new design;
FIG. 2 is a front elevational view thereof, wherein the rear elevational view, the top plan view, and the bottom plan view are identical thereto;
FIG. 3 is a front elevational view thereof, wherein the broken line depiction of the bag structure is for illustrative purposes only and forms no part of the claimed design; and,
FIG. 4 is a right side elevational view thereof, wherein the left side elevational view is identical thereto.