Belle Harris' />

An elderly woman has had to settle for a slower ride after a cheeky driver stole her mobility scooter and left her "an old clunker".

Belle Harris, from Tauranga, parked her electric scooter outside the Countdown supermarket in Greerton last week.

When the 88-year-old returned half an hour later with her groceries, she found her shiny Ranger - top speed about 7km/h - had been taken and a older, shabbier model left in its place.

"It can't have been an accident. I suspect someone's gone for an upgrade," she said.

The older Ranger had a shaky seat, crooked handlebars, a rusty basket, a cracked light and a duller shade of cream paint.

"And it's noisier," Mrs Harris said. "Even a dottery idiot would realise it wasn't theirs when they sat on it."

She said police had told her to drive it until hers was found. Her key fitted both scooters.

"I was a bit annoyed at the time. It's a mean thing to do. But at least I'm still mobile, even if it is this old thing."

Mrs Harris said she depended on her second-hand, $3000 scooter as she had sore feet and could not walk far. It was not insured.

She said police were relishing the challenge of tracking down a suspect for "grand theft scooter".

The battery allowed only 10km of travel, so she guessed the thief couldn't have gotten far.

"If I saw them, I'd run after them. But I need my scooter to do that, and this one's slower."

The scooters did not have registration or serial numbers. But Mrs Harris said there were few of the Canadian-made scooters in her community, so picking one out on the street would be easy.

A new version of her Ranger could cost up to $8000, she said, as they were solid, durable and quick.

Countdown staff said they suspected an elderly man who had visited the supermarket on a scooter previously.