I cannot help you with a shop in Singapore, but I do question the need of a high quality bike for a 6 year old child. A child that age will be able to use a properly fitted bicycle for 2 - 3 years maximum before they have out grown it. If it were me, I would get them an inexpensive juvenile bicycle that they could use while learning the proper and safe way to ride, and replace it with another that fits better as needed until they stop growing, and then replace that one with a great quality bike. As for good bikes, Specialized makes good quality juvenile bikes, but they are a much more expensive than comparable department store bikes.