Have you considered talking to some of the PR Agencies so that they can distribute it to their lists, with the benefit that they are always up to date? In my previous life we used PRNewswireAsia and were happy with the service. A release, with some follow-up, to the HK media in English and Chinese costs about HK$2500 for a commercial organisation, but I guess they might have deals for charities. I'll PM you the contact details I had (which I see from their website is still the right person).