  We show that spin $S=1$ system with large and random single--ion anisotropy
can be at low energies mapped to a $S=1/2$ system with random magnetic fields.
This is for example realized in
\mbox{Ni(Cl$_{1-x}$Br$_{x}$)$_2$-4SC(NH$_2$)$_2$} compound (DTNX) and therefore
it represents a long sought realization of random local (on-site) magnetic
fields in antiferromagnetic systems. We support the mapping by numerical study
of $S=1$ and effective $S=1/2$ anisotropic Heisenberg chains and find excellent
agreement for static quantities and also for the spin conductivity. Such
systems can therefore be used to study the effects of local random magnetic
fields on transport properties.
