A portable compressor for a tire repair kit comprises an adaptor mobile or removable from a force transmitting use position, the adaptor having an upper edge projecting with respect to an outer side wall of the compressor and defining a seat for a container of sealing fluid, the upper edge being spaced in use from a surface on which the compressor rests; and being configured to define a side support by means of a force transmission to the compressor to oppose an excessive inclination of the container of sealing fluid during the injection of sealing fluid by means of pressurized air.