  Supermassive black holes (SMBHs) can be ejected from their galactic centers
due to gravitational wave recoil or the slingshot mechanism following a galaxy
merger. If an ejected SMBH retains its inner accretion disk, it may be visible
as an off-nuclear active galactic nucleus (AGN). At present, only a handful of
offset AGNs that are recoil or slingshot candidates have been found, and none
have been robustly confirmed. Compiling a large sample of runaway SMBHs would
enable us to constrain the mass and spin evolution of binary SMBHs and study
feedback effects of displaced AGNs. We adapt the method of varstrometry --
which was developed for Gaia observations to identify off-center, dual, and
lensed AGNs -- in order to quickly identify off-nuclear AGNs in optical survey
data by looking for an excess of blue versus red astrometric jitter. We apply
this to the Pan-STARRS1 3pi Survey and report on five new runaway AGN
candidates. We focus on ZTF18aajyzfv: a luminous quasar offset by 6.7 $\pm$ 0.2
kpc from an adjacent galaxy at $z$=0.224, and conclude after Keck LRIS
spectroscopy and comparison to ASTRID simulation analogs that it is likely a
dual AGN. This selection method can be easily adapted to work with data from
the soon-to-be commissioned Vera C. Rubin Telescope Legacy Survey of Space and
Time (LSST). LSST will have a higher cadence and deeper magnitude limit than
Pan-STARRS1, and should permit detection of many more runaway SMBH candidates.
