according to the maritime memorial website, there was a wooden memorial on tong koo island:
'Sacred to the memory of Mr. B.L. Adams (Mate) Mr. W.H. Daniel (Mate) Mr. E.J. Kingswell (Carpenter) George Smith and Thomas Needham (Marines) and John Tesdell (Seaman) Late belonging to His Britannic Majesty's Ship Imogene Who fell a sacrifice to a malignant fever contracted at Whampoa in September 1834. This monument is erected to their memory by their sorrowing shipmates. May they rest in peace.'
tong koo island appears to be Lung Kwu Chau. There was a cultural heritage impact assessment done on the island but it doesn't appear to mention the memorial, which presumably faded away a long time ago.
wonder if anyone's heard anything about it, or if there's still any trace?
http://www.epd.gov.hk/eia/register/report/eiareport/eia_0812002/Final%20EIA/Html/sect_6.htm