I don't have a specific name to recommend right now, but I'd suggest posting in the Sengkang/Punggol residents Facebook groups because mums there are usually very helpful and quick to share their contacts. You can also try asking at your nearest polyclinic as they sometimes have a list of resources or can point you in the right direction lah. Word of mouth really is the best way to find a good nanny, so keep asking around and I'm sure something will come up soon!