We construct interfacial solitary structures (spots) generated by a bistable chemical
reaction or a non-equilibrium phase transition in a surfactant film. The structures are
stabilized by Marangoni flow that prevents the spread of a state with a higher surface
tension when it is dynamically favorable. In a system without surfactant mass
conservation, a unique radius of a solitary spot exists within a certain range of values
of the Marangoni number and of the deviation of chemical potential from the Maxvell
construction, but multiple spots attract and coalesce. In a conservative system, there is
a range of stable spot sizes, but solitary spots may exist only in a limited parametric
range, beyond which multiple spots nucleate. Repeated coalescence and nucleation leads to
chaotic dynamics of spots observed computationally in Ref. [1].