The most recent handover was minimal, yes. I'm more curious as to whether any single organization in Hong Kong existed prior to 1842 that still exists today, thus having survived two sovereignty changes.
Macau would probably be a better subject if that's your aim. There was almost nothing in Hong Kong before the opium wars -- a couple of thousand people in fishing villages -- but the Portuguese were in Macau for ~400 years. Unfortunately, I'm not very well versed on the latter.
I imagine that it would be even easier to look at European companies, as there has been lots of border changes there.
According to a quick search into Finnish companies, the currently oldest one (Fiskars, founded in 1649) has survived the transitions from Swedish rule to Russian rule (1809) and to independence (1917). The owners have changed several times. The oldest one that remained in the same family seems to be Frenckells printshop, which survived from 1642 to 2008.
