  We present a dual isotope magneto-optical trap (MOT), simultaneous
sub-Doppler laser cooling, and magnetic trapping of a spin-polarized
$^{39}$K-$^{40}$K Bose-Fermi mixture realized in a single-chamber setup with an
unenriched potassium dispenser as the source of atoms. We are able to
magnetically confine more than $2.2\times10^5$ fermions ($F=9/2\,m_F=9/2$) and
$1.4\times10^7$ bosons ($F=2\,m_F=2$) with a lifetime exceeding 1.2 s. For this
work, we have developed a versatile laser tailored for sub-Doppler cooling of
all naturally occurring potassium isotopes and their mixtures. This laser
system incorporates innovative features, such as the capability to select an
isotope by activating or deactivating specific acousto-optic modulators that
control the light seeding tapered amplifiers. Switching between isotopes takes
$\sim$1 $\mathrm{\mu}$s without any mechanical adjustment of the components. As
a final step in characterizing the laser system, we demonstrate sub-Doppler
cooling of $^{41}$K.
