I bought mine at a swap meet for $20. My Pontiac friend gets them from the junkyard almost every time we go. The came on MANY MANY GM models over the years and he gets them for $5.

We just look at all the cars and always find at least one. The last one found was off of a early 80s Camaro. Just be sure it's 7 blade and 19" from tip to tip and be sure the clutch spins free...