Try Craigslist in your region. You never know what might become available on there.
Around here, A.K. McCallum has been a great company to deal with for a long time for everything jon boat. They're based in Fayetteville, North Carolina, though I'm sure they would ship anywhere.
A.K. McCallum Co. - New & Used Boats, Service, Parts and Financing in Fayetteville, NC, near Eastover and Fort Bragg
Hope this helps.
Jim