We propose a search for B meson decays to a baryon plus missing energy at the Belle II experiment to probe supersymmetry with a GeV-scale lightest neutralino χ~10 and R-parity violation (RPV). We perform analytic computations of the signal branching fractions in the framework of effective field theory, with a single nonzero RPV operator λij3′′U¯icD¯jcD¯3c, where i, j = 1, 2. The hadronic form factors are calculated using an SU(3) phenomenological Lagrangian approach for the proton, as well as several hyperons and charmed baryons. Since the decay of the neutralino is kinematically and CKM suppressed in this theoretical scenario, it decays outside the detector and appears experimentally only as missing energy. We detail the analysis techniques at the experimental level and estimate the background in the B+→pχ~10 search using published results for B+→ K+νν¯. Our final sensitivity plots are shown for both λ113′′ versus the squark mass mq~ and λ113′′/mq~2 versus the neutralino mass mχ~10. We find that the search at Belle II could probe λ113′′/mq~2 down to the order of 10−8 GeV−2 in the kinematically allowed mχ~10 range. We also obtain current limits on λ123′′ by recasting an existing search interpreted as B0→Λ0χ~10, and comment about searches for B+→Σ+χ~10, B0→Σ0χ10, B+→Λc+χ~10, and B+→Ξc+χ~10. In closing, we briefly discuss potential searches at the LHCb and BESIII experiments.