I am having the dangdest time finding someplace with a wheel stud for this trailer hub. Any ideas. I bought the trailer used and found one of the wheels studs 1/2 a lugnut too short.

Welcome to the forum...

Is the thread a odd size?  Likely the hardest part will be driving the old stud from the hub.  I would recommend taking the hub off the axle.  Otherwise, you risk damaging the bearing pounding on the stud trying to get it out.  Then, you can take it to a local machine shop and press the stud from the hub.  Wheel studs are common in various lengths.