Detective Sergeant Darren Pritchard said the man sought medical help and had to have one of his fingers amputated.
"This was a random, unprovoked attack on an innocent elderly man and we are keen to find out who was responsible," Mr Pritchard said.
Police would like to speak to anyone who may have seen people acting suspiciously around the Big Save/Ahuriri business park area early on Saturday morning.
One of the men being sought is described as a large thick-set dark-skinned male with a round face. The other male was of slighter build.
Anyone with information about the incident should contact Mr Pritchard at HB Police on 06 8310700 or information can be left anonymously on Crimestoppers 0800 555 111.