John Key did it with his right, now Rotorua businessman Chris Smith is doing it with his left - arm that is.

The owner of Chris Smith Glass broke his left arm over Christmas and has decided to follow in the Prime Minister's footsteps by seeing how much money he can raise for charity by auctioning his cast on online auction site TradeMe.

The successful bidder will win the bright blue cast, propped up and mounted in a glass cabinet, with all money raised going to the Rotorua Community Hospice.

The cast has already has the signatures of Rotorua MP Todd McClay, Tiger Woods' golf caddy Steve Williams, singer Elizabeth Marvelly, Olympic cyclist Sam Bewley and former All Black Bill Davis.

It's hoped other "celebrities" will sign it before the auction closes on February 20.

"I'm not expecting to raise anywhere near what John Key got for his but even if it's just $50, it will be nice to give something to Hospice," Mr Smith said.

"They always need support and I believe in keeping things local."

Wellington businessman Ganesh Cherian, paid $18,500 for Mr Key's cast. The money was donated to the Fred Hollows Foundation to pay for cataract operations in the Solomon Islands and up to 400 people are expected to benefit.

While Mr Key broke his arm falling at a Chinese New Year celebration in Auckland, Mr Smith's injury was a little less public.

He was walking a dog along Moncur Dr over Christmas, slipped and fell on his arm. It was "a bit sore" but he never imagined it was broken and didn't seek any treatment until this month when it "really started giving me some grief" during a golf tournament. He was subsequently told he had a break just above his wrist. Mr Smith started his online auction on Tuesday and by yesterday his cast had attracted seven bids, with a top bid of $30. Rotorua Community Hospice chief executive Tracey Watters said she was thrilled Mr Smith had picked hospice as his charity of choice. About 70 per cent of its funding comes from the Lakes District Health Board. The rest has to be raised in the community.

"Even if only $70 is raised it's $70 that might pay for someone to receive a visit from a hospice nurse once and we might not need to see that person again for several years," Ms Watters said.

* To place a bid on Chris Smith's cast on TradeMe, search under art and cast. The auction closes on Friday.