  Building on our recent proposal to explain the experimental hints of new
physics in $B$ meson decays within the framework of Pati-Salam quark-lepton
unification, through the interactions of the $(3,1)_{2/3}$ vector leptoquark,
we construct a realistic model of this type based on the gauge group ${\rm
SU}(4)_L \times {\rm SU}(4)_R \times {\rm SU}(2)_L \times {\rm U}(1)'$ and
consistent with all experimental constraints. The key feature of the model is
that ${\rm SU}(4)_R$ is broken at a high scale, which suppresses right-handed
lepton flavor changing currents at the low scale and evades the stringent
bounds from searches for lepton flavor violation. The mass of the leptoquark
can be as low as $10 \ {\rm TeV}$ without the need to introduce mixing of
quarks or leptons with new vector-like fermions. We provide a comprehensive
list of model-independent bounds from low energy processes on the couplings in
the effective Hamiltonian that arises from generic leptoquark interactions, and
then apply these to the model presented here. We discuss various meson decay
channels that can be used to probe the model and we investigate the prospects
for discovering the new gauge boson at future colliders.
