I bought the Stainless Steele ones from Kincaid Gardens. They come in bundles of 25 pieces and the prices depends on size and quantity ordered.http://www.kincaidgardens.com/Signature_Plant_Markers-Plant_Markers_P_Style.html
I also buy the wire ones from Everlast label company
http://everlastlabel.com/
To make the galvanized wire last longer you can dip them in Plasti Dip. It's the rubber type stuff that is on tool handles. You can get a container of it at places like Home Depot and you just dipp the wires in it to coat it (just make sure you have the nameplate already on them).