Might be cheaper/easier to create your own. Can you go to your state's DMV's data base to look up vin numbers? (you can in Illinois). Pick a number that's not already in the database, stamp it onto a piece of metal, weld it to the bottom of the neck, & your set.
In Illinois, if you build a homemade trailer, they just issue a new number which you have to affix to the trailer frame.
Mike Sal