If you mean for a cot or crib, we went for natural (chemical free process) latex/rubber core with organic cotton and wool.
Couldn't find that exact spec anywhere in HK or even Australia and had to order it from the US online in the end. The site doesn't seem to be up any more, but the email for the owner is [email protected]. It's great and the difference between the latex and the one that the cot came with is huge. You just have to make sure you have a US sized cot.
I did speak to Organic Baby in Causeway Bay and they were thinking of stocking them in the future - so you could try them first.
We got ourselves a king size natural latex mattress from Okokoo at Ap Lei Chau - not cheap, but worth it for the great sleep!