I did the same thing to an old utility trailer i had. i bought the steel for the tongue at a steel place in Manchester, NH. I can't remember the name of the place but is right behind the 7-11 Store at the intersection of Brwon Avenue and Queen City Avenue. I was in and out of there in about 3 minutes with what I needed. The guy just pulled it off a cull/scrap pile he had in the yard. And it was very cheap.
Hey Bill throw me a shout on my cell tomorrow Rob's dad deals in scrap metal, I bet he could come up with a piece for ya. Give me a call Take Care God Bless LOL Dave