Near-field multiple-input multiple-output (MIMO) radar imaging suffers from high computational load inherently due to irregular spatial sampling with distributed antennas. Existing acceleration methods for near-field MIMO imaging typically rely on interpolation or compensation of measurements and are primarily developed for direct reconstruction. This hinders their ease of adoption for different MIMO geometries and requires further modification for regularized inversion. In this study, we address these challenges by developing a fast regularized reconstruction approach for three-dimensional near-field MIMO imaging based on the Stochastic Proximal Gradient Method. We demonstrate the performance of the developed approach through experimental measurements. The results show a significant improvement in runtime without any notable compromise in reconstruction quality.