When real estate professionals talk about the boom in shared office space, most think of WeWork. But the $10 billion unicorn is only one of dozens of companies vying for market share in New York City. The Flatiron District alone is home to 26 coworking spaces run by 20 different companies, according to a new report by the Flatiron 23rd Street Partnership, a local business improvement district. Some, like WeWork’s 108,000-square-foot space at 79 Madison Avenue, take up multiple floors. Most, like the 36,000-square-foot AlleyNYC at 119-125 West 24th Street, are smaller.