If you want to block specifically the blebbing, you need inhibitors of ROCK or regulatory Myosin Light chain. Y-27632 blocks ROCK and ML-9 blocks rMLC. Good Luck..!!
Is blebbing always a myosin based process? On that same note, does exocytosis of vesicles outside of a cell require myosin or is there another mechanism that I should research?
Myosins play the "bleb neck constriction" role in blebbing process (like actomyosin in muscle contraction). A similar role is well documented in cytokinensis.