What improvements are available for apartments?

In Sleeping Dogs, you can purchase improvements for your apartments. So far I've found a new bed, a sound system, a bird and AC in the Night Market for the North Point apartment and a furniture package at K-Bar for the Central Apartment.

North Point apartment

• A brand new bed, a massive sound system, a pet bird and an air conditioner are sold in the Night Market, make sure to check the back streets for the sound system.

Central apartment

• A furniture package including a table and a rug is sold at K-Bar for the Central Apartment.
• A sofa set is sold by a man at the Boardwalk, northeast Central.
• A tapestry is sold by a man inside Wah Fi Storage in the middle of Central, the entrance is on the eastern corner, just southeast from the nearby clothing shop.
• An ancient vase is sold by a woman behind the westernmost building of Government House in Central.

Aberdeen houseboat

• A vendor at the waterfront market to the NNNW of your houseboat sells an awesome pet bird, there's a massage parlor nearby.
• Some stolen art is sold by a man in a black suit behind the house down the second wide ramp to the west of the awesome pet bird vendor.
• A giant movie poster is sold by a man south of Warehouse in Aberdeen. Take a right off the bridge as you approach Warehouse from Kennedy Town Beach and you'll find him.
• A strange idol is sold in Aberdeen, just south and up the stairs from the apothecary.

Kennedy Town house

• A hot tub is sold by a man inside a small area south of your house, turn left as you're leaving the house and he will be immediately to your right, near the Sun Yat Housing Complex.
• Plant service is offered by a woman nearby to the hot tub seller, behind a corner on the foot road going south through the Sun Yat Housing Complex.
• A fish is sold by a man standing opposite of the car seller in Kennedy Docks.
• An idol of Guan Yu is sold by a man standing near a building with 2 red flags called Kennedy Pier (not marked on the map), a short distance to the west from where the highway leaving Kennedy Town meets the road leading to the Cemetery.

The following video has been instrumental in finding the rest of the upgrades, use it if the above instructions aren't enough.

Also, an idol is sold in an alley, up some stairs, betwen the map text of Aberdeen area and the apothecary marker. (you go there with Jackie on a certain mission).

The hot tub is sold by a guy in a small park, just at the bottom of the road that goes to the kennedy apartment on the left, up some steps. It is where the drug bust is, and you have to do the bust to be able to talk to him (as soon as you get there, the guys will start shooting at you).