"Mosheh Ish Horovits" can be transcribed  "Mosheh ish Horovits," but the "Ish" can also be capitalized as  an "epithet"
(like "Alexander the Great").

The established form should be "Horovits, Mosheh".

One should make a  ref  from it  as  if from a compound surname ("Ish Horovits, Mosheh") and another one as if from the 2nd part of the compound  surname  ("Horovits,  Mosheh  Ish")--  if  that  varied sufficiently from  the heading.
Another possible ref  is "Mosheh,$cIsh Horovits".