New or Used ?

http://www.flaman.com/trailers/Ag-Transport-Trailers/Trailtech/Sprayer-Trailers-58/

http://www.trailtech.com/product_sprayer.html

http://www.sandstrailersales.com/INVENTORY/NORTHLOT/CombineTrailers.aspx

AuctionTime previous sales

http://www.auctiontime.com/listings/trailers/auction-results/online/list/category/860/agriculture-equipment-transport-trailers?OALResults=1

Some current ones

https://www.truckpaper.com/listings/trailers/for-sale/list/category/860/agriculture-equipment-transport-trailers