I have checked all the aquarium shops at the famous aquariums at Clementi Blk 328 (also known as C328 LFS). They do not carry the Python Water Changer or similar products such as the Aqueon Aquarium Water Changer.
Hence, the most probable way of getting the Python No Spill Water Changer is through Amazon:
25 Foot – Python No Spill Clean and Fill Aquarium Maintenance System
I have personally purchased it and it arrived in good condition within a reasonably quick time. Some photos are attached below, with a stack of A4 paper as a size comparison.
There is also a related product by Aqueon that works basically the same way. According to online reviews it is also good, but possibly not as good as Python.
The benefits of these water changers is that they can not only fill the tank (a simple hose can already do that), but they can also draw water out of the tank, without using electricity. Basically they use suction from the tap (siphon effect) to draw water out.
Not sure why Singapore aquariums (LFS local fish shops) do not import these products as it seems quite a time saver and reduces the need for carrying buckets.
Note that online stores (such as Qoo10 or Lazada) may appear to carry these items, but at a much higher price than if you purchase from Amazon directly. The reason is that they are from dropshippers — when you order from them, they will act as the middleman and order from Amazon to send it to you.
A video to demonstrate how it works: