  We report the discovery of a z=2.65 low-ionization iron broad absorption line
quasar, FIRST J100424.9+122922, which is gravitationally-lensed by a galaxy at
z~0.95. The object was discovered as part of a program to find very red quasars
by matching the FIRST radio survey with the 2-MASS near-infrared survey.
J100424.9+122922 is the second lensed system to be found in this program,
suggesting that many gravitational lenses are probably missed from conventional
optical quasar surveys. We have made a simple lens model and a rough estimate
of the reddening in the immediate environment of the quasar which suggests that
the quasar is intrinsically very luminous and is accreting at close to the
Eddington limit of its ~10^9 M_sun black hole. The lensing galaxy has a small
amount of dust which is responsible for some excess reddening observed in the
fainter image of the quasar, but is otherwise a fairly typical massive
elliptical galaxy. We model the selection effects working against the detection
of red quasars in both lensed and unlensed samples. We show that these
selection effects are very effective at removing even lightly-reddened high
redshift quasars from magnitude-limited samples, whether they are lensed or
not. This suggests that the red quasar population in general could be very
large, and in particular the class of iron broad absorption line quasars of
which J100424.9+122922 is a member may be much larger than their rarity in
magnitude-limited samples would suggest.
