The Health Food Store, Life, in DB Plaza has deliveries on Thursdays. You can also leave your number for them to call you when deliveries arrive.
Alternatively, head to the Graham Street local market - the larger shops that supply restaurants in the Soho area stocks them on a regular basis.
Another option is the Health Food Store on Stanley Street (Central), close to the escalator to Mid-Levels.
Usually around HK50-60 per bunch for 8-10 stalks.
Hope this helps.

Thanks both. The one in NSW. Is that Chinese kale or curly kale?

Order it directly from Brian at Green Vitamin. Just google greenvitamin hk and you will easily find his website. He grows kale in Hong Kong. Just Green has kale from him except that it usually already looks terrible when Just Green sells it.

Brian also has a lot of other delicious products.

Last week I bought a lovely box of baby kale, organic, in DB Wellcome. With the boxes of salad leaves and baby spinach. It was $49.90 but was fresh and delicious!

I saw that The Store sells Kale chips. They have an Internet website and a real shop next to the escalators on Cochrane St, Central.
The Kale chips are very good, they have like 4 different flavors! You should try some