A continuing difficulty with the core dynamo hypothesis for the origin of lunar paleomagnetic fields is the small maximum size of a present-day iron core and correspondingly small estimates for maximum lunar surface paleofields based on available models for planetary magnetic field generation. This paper explores the possibility that magnetic fields may be significantly amplified or generated in large-scale meteoroid impacts and that these fields may have contributed substantially to the observed magnetization of lunar materials. Using a one-dimensional numerical model for expansion of impact-produced vapor clouds, scalar electrical conductivities for the expanding partially ionized gas are calculated to be in the range 100-106 S m-1 for meteoroids with representative compositions impacting at velocities greater than the thresholds for significant vaporization (~10 km s-1). Magnetic diffusion will therefore be small in comparison to advection on relevant time scales. The available gas kinetic and internal energy densities are ≫ probable magnetic energy densities for time periods that increase with increasing impactor velocity and size. These periods represent limits on the time available for magnetic field amplification/generation and are in the approximate range 102-104 s for meteoroids with radii between 1 and 200 km impacting at 15 km s-1. Preexisting solar wind magnetic fields will be compressed by the expanding plasma cloud and amplified by induction in the presence of an electrically conducting lunar interior. Within the limitations of the one-dimensional modeling results, maximum surface field amplitudes expected via these mechanisms are ≲0.01 G so that their importance with respect to lunar paleointensities (0.01--1.0 G) is marginal. However, existence of a core dynamo during the 3--4 b.y. time period with probable surface fields of ≲0.003 G would increase maximum induced field amplitudes to values compatible with the range of lunar paleointensities. Direct generation of transient fields in impact-produced plasmas via currents forced by thermal pressure gradients will occur, but estimated field amplitudes for large-scale impacts (~10-4-10-5) are too small to contribute to lunar paleointensities. Dynamo amplification of these fields as a result of expansion velocity gradients and turbulence within the expanding plasma cloud is possible within available time periods, but necessary conditions for achieving lunar paleointensity amplitudes have not been demonstrated.