UHECRs at the most extreme energies provide strong constraints on their possible origins. They have a smaller horizon due to energy losses during propagation and are less deflected by intervening magnetic fields. However, studies searching for correlations with nearby sources are limited by the rarity of these events, and the suggested source catalogues often fall short in explaining their origins. We propose to use the reconstructed properties of individual detected UHECRs to map out three-dimensional constraints on the locations of their unknown sources. In this work, we focus on the recently published catalogue of 100 events with energies from 78 to 166 EeV recorded by the Pierre Auger Observatory and use CRPropa 3 to model all relevant propagation effects, including deflections in the Galactic and extra-Galactic magnetic fields. In deriving our location maps, we consider the reconstructed energies and arrival directions of events as well as results on the UHECR composition. We present constraints on the source locations for some of the most restrictive cases and demonstrate the impact of uncertainties in the reconstructed UHECR properties on these results. We also highlight possible astrophysical sources that are compatible with these regions and requirements. This complementary perspective lays the groundwork for building more physically-motivated source catalogues and statistical analyses in the future.