A Tauranga father is hoping to retrieve a compact yet pricey piece of technology vital to his daughter's diabetes management.

Chris Toefield's seven-year-old daughter, who has type one diabetes, is believed to have dropped her Dexcom CGM device as the family made their way into Saturday's Christmas in the Park event.

A Dexcom CGM device, similar to the one pictured, is believed to have been lost at Blake Park's Christmas in the Park event on Saturday.

The device, no bigger than an ordinary mobile phone, is used for continuous glucose measurements at a cost of about $1000.

Type one diabetes is an 'auto-immune' condition most often occurring in childhood, often in children aged 7–12 years.

Chris thinks the device, in a small leather pouch, has fallen out of his daughter's bag outside the Blake Park entrance to the festive event on the side of Maunganui Road at around 2pm on Saturday.

'It's completely useless for anyone else and it's used to receive blood glucose measurements,” he explains.

'It's a very important part in diabetes management.”

The device has Chris's wife Temple Mayfield's name and cell phone number on it.

It reads: Temple Mayfield 027 671 8951.

Anyone who may have picked up the device or has information are asked to call Chris on: 022 150 1058.