Thanks to Paul Bonneau, Bert Fox, and Alfred Jorgensen for this information.
If your front brake light switch needs replacing, here are a few sources:
Your local Moto Guzzi dealer may have it in stock for 5 or 6 bucks.
Radio Shack item number 275-016, SPDT Switch w/o Roller (This will require slight modification to remove the lever and reduce the width of the terminals)
Radio Shack item number 275-017, SPDT Switch with 3/4" Roller Lever (This will require slight modification to remove the lever and reduce the width of the terminals)