There is a shop known as "antry Magic" at Casuseway Bay. They offer a lot of utensils used in baking. This shop used to be @ Pedder Building Central. Causeway Bay shop is newly opened. It is just opposite Lee Garden along Hysan Rd.
Maybe you can call them up to see if they have what you need first. Sorry i don't have their number, they have a website as well.
I just been there yesterday to get some stuff for the kitchen, the pricing is ok.