Entrepreneurs invent what they can't find

— -- Katie Danziger, mom to a baby who "tended to throw up a lot," craved an easy-to-clean car-seat cover.

Todd Greene, who liked his scalp stubble-free, wanted a razor that effectively sheared his bald head. He created the HeadBlade.

Nick Hill, owner of an outdoor-loving cat, needed a pet door that let his feline, Flipper, re-enter his home but wouldn't let in any other creatures.

None could find the exact product or service they wanted. So they created their own, then went on to successfully sell their designs commercially.

Deemed "user entrepreneurs," these folks don't just chat about their innovative ideas. They take action to solve a personal or business need, then aim to profit off their concepts.

A new report from the entrepreneur-focused Ewing Marion Kauffman Foundation— based on one of the largest-ever surveys of new businesses — says 11% of U.S. start-ups that survive five years are founded by user entrepreneurs.

"This is a fairly wide-ranging phenomenon," says E.J. Reedy, co-author of the Kauffman report. "If you're not seeing a product or service offered to you, that's often the spark that sets someone off down an entrepreneurial path."

Sara Blakely, founder of the Spanx body-shaping hosiery empire, is one such entrepreneur. In 1998, she planned to wear cream-colored pants to a party. She wanted a smooth, svelte figure with no visible panty lines — and didn't want her sandal-clad feet covered by stockings.

To create that look, she cut the feet off a pair of control-top pantyhose — and with that, a business idea was born. Blakely invested $5,000 from her savings, researched manufacturers and launched a fledgling body-shaping hosiery firm.

Customers snapped up her products, and Blakely, now 41, was just named the youngest self-made woman on Forbes' "The World's Billionaires" list.

On a smaller scale is Elizabeth Thurer, whose business is also based on a fashion plight. Back in 2007, the then-stay-at-home mom couldn't find a button-front shirt that was both comfortable and smart-looking. Thurer sought out designs and fabric, and had a tailor sew up a couple of shirts.

Thurer thought the shirts would solve her wardrobe problems and that she could sell a few to friends, but demand grew. In 2011, she partnered with another woman, Lisa Daniel, and last fall, they launched the Elizabeth Daniel New York clothing line in stores and online.

Initially, there wasn't thought of creating a big business out of it, Thurer says. "Then I realized I could do this as a legitimate business."

User entrepreneurs come in many forms, from doctors who market new medical devices to technophiles who create innovative software, says Sheryl Winston Smith, co-author of the "user entrepreneur" report.

"There are examples in all sorts of industries, from high-tech to juvenile products to sporting equipment," she says. "It's very much a diverse group of people and ideas."

And no matter the inspiration, it usually takes some research, funding and passion to go from idea to execution, she says. "Then it's just being willing to take the leap and actually doing it."

Tips for those who want to make that jump: