Hicarer 2 Pcs 1/2 Inch Pipe Repair Clamp with Single Bolt Stainless Steel Clamps Copper Pipe Repair Kit(Classic,3 Inches Length)

Can you access the pipe at the other side of the duct? This is a difficult spot to cut. A hose clamp over rubber might stop the drip for a while. Here is an example. I have not used myself. https://a.co/d/01IotVyM I am DIY