Another possible method of steering is to build four or more reaction jets around the rocket; could be fed with a monopropellant or exhaust from the main engine or its turbopump.
If you can deal with slight decreases in thrust, you can also do thrust vectoring with injecting water or other suitable liquid into the nozzle in proper places. Could be mechanically simpler than gimbals in some cases.
Another possible method of steering is to build four or more reaction jets around the rocket; could be fed with a monopropellant or exhaust from the main engine or its turbopump.