iPhone accessory makers are getting an unexpected boost from Apple Inc’s recommendation that users buy a case to fix a glitch on their phones.

“It is good news,” said Tim Hickman, founder and chief executive officer of Hard Candy Cases in San Francisco. Apple’s suggestion may add allure to an already popular accessory, he said. “The demand is there and Apple has built it.”

Apple made the recommendation after last week’s debut of the iPhone 4, which drew complaints that it loses reception when held a certain way. The company advised customers to hold it differently or use a case. While that solution has irked some buyers, it could benefit Hard Candy, Belkin International Inc. and other accessory sellers — including Apple itself.

The cases, typically made of rubber, plastic or recycled materials, are already part of a growing market. Mobile accessories generated $135 million in US revenue in the first quarter, according to NPD Group Inc. That indicates annual sales of more than $500 million.

‘Thong Underwear’
Apple is selling its own iPhone 4 cases in six colors for $29 each. They’re made of a piece of rubber known as a “bumper,” which surrounds the outer rim of the phone. The accessory doesn’t cover the back or front of the device, prompting the iPhonesavior.com blog to call it “the thong underwear of protective iPhone fashion.”

Shaw Wu, a San Francisco-based analyst with Kaufman Bros.LP, said Apple may have to start giving away the bumpers with the purchase of a phone as a way to alleviate customer concerns.

Accessory sales are “almost pure profit” for the company, said Wu, who recommends investors buy Apple stock and doesn’t own it himself.

“The meat and potatoes of their business are still core products — the accessories are the gravy,” he said.

Natalie Harrison, a spokeswoman for Cupertino, California- based Apple, declined to comment beyond the company’s remarks on the antenna last week.