Blower resistor replacement kit
The resistor itself is generally available at places like Autozone or Advance Auto stores. In my case, the terminals on the resistor and the plug (pigtail) for "speed 2" were corroded beyond repair, so I needed to replace both, and the pigtail is a little harder to find. Dorman sells a kit (their part no. 973-411), that includes both the resistor and the pigtail, which I ordered online from Advance Auto. To install the pigtail, you'll have to cut the wires to the old pigtail (keeping track of which wires go to which connections!), and splice them to the replacement pigtail.