is prob a good starting point. off top of my head 3 girls there that fit the criteria are: crystal, sammi and doris. miko also has a sizeable ass as well iirc.
another thing u can try to do is just goto a walk up location with alot choices, and scan thru. pay close attention to girls in bikinis or form fitting outfit that shows off the hip-waist ratio. fuji, jsl, king hing and the likes will have enough selections that u can prob find one that tickles ur fancy..
good luck with your hunt and pls share with us ur findings. i am always on the look out for next great ass in hk. nice boobs are dime a dozen here, but a real juicy bubble butt is such a rare treat.