View source for Omitting theories of undefinable sets

Suppose $M$  is  countable recursively saturated and
$X$ is an undefinable subset of $M$. Is there a countable recursively saturated  $N$ such that $N$ is an elementary end extension of $M$,
and if $Y \subseteq M$ is coded in $N$, then $(M,Y) \not\equiv
(M,X)$?


The answer if `yes' is either $(M,X)\not\models PA^*$ or ${\rm Th}(M,X)\notin {\rm SSy}(M)$.

This problem is listed in Kossak, Roman; Schmerl, James H.
The structure of models of Peano arithmetic.
Oxford Logic Guides, 50. Oxford Science Publications. The Clarendon Press, Oxford University Press, Oxford, 2006. xiv+311, but, unfortunately, with many typos.