High concentrated H2O2 has it's own drawbacks. Hard to obtain above 30% unless you order a tanker truck worth, needs a catalyst to decompose but will happily oxidize most catalysts unless you use an expensive one like platinum and last, any contaminate will happily act as the catalyst at the absolute worst time.
If I were to try RCS at the hobby level, I'd go with a high pressurized gas. You can buy CO2 at ~2000psi along with supporting hardware (tanks, fittings, etc) from a paintball store. There are also tanks designed for ~3500psi to ~4000psi compressed air for precharged pneumatic air rifles and the pumps to fill them. You'd need fast acting gas valves (solenoids?) as well as a regulator to step the high pressure down to a level the valves can work at.