Cyclists may be adding a recently invented item to their wish list this holiday season — chainless bikes.Trek Bicycle is introducing two new models in December that operate on carbon fiber composite belts instead of chains, making Trek the first to use this technology for mass production.”With the exception of the cool factor, [the belt] is going to decrease noise, and it’s not going to build up dirt,” said Mark Adams, manager of Capitol Cyclery. “It’s going to be lighter, and it won’t rust.”Adams said the new bikes are virtually maintenance free, and owners won’t be bothered with the hassle of replacing greasy chains.But Adams said the bikes could get a little pricey. The District, a single-speed version of the chainless bike, will cost consumers about $930.