I bought a Glacier Bay bathroom faucet from Home Depot. The model # 409C-0301. It is not working properly after being installed for one year. Water keep running while it is in the closed position. I was told by my plumber to purchase the faucet cartridge, but I cannot get it buy. Can you tell me where I can get it online?

Glacier Bay faucets are carried by Home Depot, try them for the cartridge, I think Glacier Bay faucets has life time warranty, the number 409C-0301 you posted is not the correct P/N, call them at 800-220-3036 or 888-328-2383 contact the tech support; they will help you with the correct parts and send you whatever needs to be replaced for free, good luck.
John