The make is Zoll and the model AED-plus.
Mrs Saaristo said many club members were in their 60s with some well into their 80s, so it was vital to have the defibrillator on hand. "I think it's an unconscionable, mindless action, without a care for anyone else.
"And what on earth good is a defibrillator going to be to them?"
Mary Kay, a club member for 36 years, said she was very annoyed by the theft.
"Having a defibrillator is very important. In my age group I'm sure there's a lot of people with heart trouble."
Mrs Kay and other club members had had lessons in using the heart-starter even before the club had raised the money.
Two more training sessions since then, led by St John medics, had been attended by up to 40 members each time.
Police Sergeant Peter Masters said the defibrillator was taken sometime between 1 and 4pm on Saturday, April 20.
The offenders may not have realised what it was or mistaken it for something else.
He urged anyone who knew who had taken the machine, or where it was now, to call the Kerikeri station on (09) 407 9211. Anonymous tips could also be passed to Crimestoppers on 0800 555 111.
The club is offering a reward for the defibrillator's return or information leading to its recovery.