  We study topological lumps supported by the second homotopy group $\pi_2(S^2)
\simeq {\mathbb Z}$ in a gauged $O(3)$ model without any potential term coupled
with a (non)dynamical $U(1)$ gauge field. It is known that gauged-lumps are
stable with an easy-plane potential term but are unstable to expand if the
model has no potential term. In this paper, we find that these gauged lumps
without a potential term can be made stable by putting them in a uniform
magnetic field, irrespective of whether the gauge field is dynamical or not. In
the case of the non-dynamical gauge field, only either of lumps or anti-lumps
stably exists depending on the sign of the background magnetic field, and the
other is unstable to shrink to be singular. We also construct coaxial multiple
lumps whose size and mass exhibit a behaviour of droplets. In the case of the
dynamical gauge field, both the lumps and anti-lumps stably exist with
different masses; the lighter (heavier) one corresponds to the (un)stable one
in the case of the nondynamical gauge field. We find that a lump behaves as a
superconducting ring and traps magnetic field in its inside, with the total
magnetic field reduced from the background magnetic field.
