Hand drums? What exactly are you referring to?
I used to be in chinese orchestra; we got our equipment from either Bras Pasah 2nd floor, or 2nd floor at Rochor Centre (opposite Sim Lim).
These are mainly the dagu, xiaogu and so on, though.
The bras pasah one is easy to find, rochor centre not so much. If time permits, I could possibly show the way there.
I don't think there are regular drum circles for Chinese drums... but there are percussion groups and there's many many orchestras in singapore.