For fellow RC friends coming to HK, you can shop your RC products at a street called: Kwong Wah Street (KWS). There are about 10 hobby stores located on or around this street. KWS is located between Yau Ma Tei and Mongkok in Kowloon. If you take the MTR, take the Yau Ma Tei exit.
Google Map Link:
https://maps.google.com.hk/maps?sadd...sz=16&t=m&z=16
Various shops will carry various products/brands, so you need to shop around. Because locally, 1/10 touring cars are popular, thus you will find more selections on touring cars. F1 and 1/12 is also decent.
As for offroads, not all shops will carry them. There are more parts for 'local/chinese' brands like Team C racing products than foreign brands like traxxas or losi for example.
As for electronics, you will find most brands like Hobbywing, SpeedPassion, LRP, Nosram, Orion etc...