I bought an universal replacement from Homedepot for $22 and it works and the leak stopped immediately.
However, it is a little smaller to fit well into the seat; so I take out a plastic cup from the old spout and mount it onto the new one. Now everything is perfect.
I noticed that the spray mode is very gentle, nothing like the old spray which is VERY strong. If you are the original owner of the faucet, Moen will send you a replacement for free. The model # for the wand is 136829.