Hey there, trtalbott.
Around here (southern Middle TN) we see them in front of antique dealers' places, out in folks' barnyards and fields, and generally in odd places. Mostly I see horse-drawn mowers, disc harrows, springtooth harrows, plows, and planters. I doubt you'll find a very good place to buy them online-- they would be very expensive to ship. You might have good luck driving through the countryside and asking gas station attendants, antique dealers, farmers, etc.
Best of luck,
Darren