What is the Westinghouse part number for Hunter 3speed fan switch with 4 wires (L, 1, 2, 3)? Available at Home Depot?

There are many on sale at HD, take the old one with you. Most will be Zing Ear switches. All 3 speed will have 4 wires. Note the color placement on the old one.

Just a hint, take a picture of the wire placement on the switch, do not trust your memory!