Fodor space in generalized descriptive set theory

We study the continuous reducibility of isomorphism relations in the space of regresive functions in ${\kappa }^{\kappa }$. We show for inaccessible $\kappa$, that if $\mathcal{T}$ is a theory with less than $\kappa$ non-isomorphic models of size $\kappa$ and ${\mathcal{T}}^{\mathrm{\prime }}$ is unstable or superstable non-classifiable, then the isomorphism of models of $\mathcal{T}$ is continuous reducible to the isomorphism of models of ${\mathcal{T}}^{\mathrm{\prime }}$.