Yes, sometimes plumbers or HVAC guys manufacture those vent connectors on-site. There are no screws permitted on double wall vent pipe connections (unless its locking design calls for a screw) except for the first connection with a single wall vent pipe, which is very common (pictures below).
Single wall vent pipe should fit into the inner tube of the double wall vent pipe. You can use longer sheet metal screw and penetrate three walls or (that would depend on the B-Vent lock design) open / bend 3 locks on the outer wall (visible on the bottom picture / next to the screw) and drive the 3 screws into the formed openings / through the inner B-Vent and a single wall vent pipe.
Let me know if there's anything elese I can help you with.