Did you try to check with this tuition agency - SchTutors Tuition Agency | Recommends only MOE School Teachers? One of close friend just engaged them for her daughter, pretty good. They recommend only MOE teachers, and they have both group tuitions and 1-1 tuitions. Hopefully this is useful.
Also, if you google "Tuition Agency MOE", they are listed as the first result so they should be reliable.