There are fishball stands literally every 5 store fronts away from each other. My favorite on is on Yen Chow & On Chau Street in the Sham Shui Po district. The yummy famous street food is of great quality here. You can taste it in the curry. You can choose from a Mild, Low Spice, or Max Spice level of sauce. Low Spice is already plenty for me to handle. Fishballs are not the only snack they have though. They also have beef brisket and squid!
Skewer HK$5 Bowl HK$20