Hi Alex, I'm fairly near to where you are - currently in the Philippines, and I've passed through Sing rather a lot on the way to other countries. Anyhow, back to the point - if you don't get any more specific replies to your query, I suggest you do a Google search for something like "aquatic shops in singapore" then check out the local results which are half-way down the first page.
Wishing you well!
Ben
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