  Various supersymmetric (SUSY) scenarios predict a sub-GeV neutralino decaying
into a single photon and an invisible state. This signature has recently been
studied in a number of intensity frontier experiments, finding constraints
complementary to the usual collider searches. In this work, we study the
prospects of searches for long-lived neutralinos coupled to an ALPino or
gravitino, where each can act as the lightest SUSY particle (LSP). In addition
to the neutralino decays into a LSP and a photon, we also consider three-body
decays into a pair of charged leptons, and signatures related to scattering
with electrons and secondary neutralino production. For both models, we find
that the searches at FASER2 will allow to overcome the current bounds, while
SHIP will extend these limits by more than an order of magnitude in the value
of the coupling constant.
