If you go to the wet market on weekends, some of the stalls that
sells fishcakes or achar do sell some home-made ones, but I can't
pinpoint exactly where. Or you can find it on the supermarket
shelves (cold food section).
One place that sells it is the Kosma food court at Bishan St 24 at
blk 280 - by the chwee kueh stall, and the hae bi hiam is not
soaked in oil.