I have a number of ' grinders ' , and the Braun or Krups coffee grinder might be one to try :
the Braun , similar price , does not seem to be made any more
then there is this one :
probably the same thing .
and
this is twice the price :
but has two blade sets .
in the case of ginger , it very fibrous , so might heat up the ginger quite a bit to get to ' fine '
if it gets there .
the 16 - 19 USD version do not have a very sharp blade , so y0ou won't dull it.
just make sure the ginger is really really dry or you won't get very fine.
good luck
P.S.: if you tried to grind the fibers down w an M+P , it might take quite a bit of effort ,
enough that you might not want to try that again .