I think there might really be not that many available. I've been window-shopping (really, just window-shopping

) and they do show up on Craigslist/Dreamhorse and mostly are sold immediately if they have some training. The dealer I bought Rowan from gets a bunch in every few weeks and they are always gone within days - they are typically from the Amish, usually trained to ride and drive, price around $800-1500 depending on training and cuteness factor.
With the horse market as nutty as it is right now I can't imagine it's going to be LESS nutty come spring so I bet you'll have no trouble selling him! minihorsesales.com is another one - it appears that horses do move off there, variably, some are really expensive so they take longer, it might not be free to list a horse though.