Unfortunately 126 film is no longer made, and even the stocks that were held on to after production ended have for the most part dried up. The good news is that you have another option, and that is to reload the 126 film cartridges with 35mm film. The 126 film was after all, just 35mm film in a more convenient roll that didn't require film leaders or rewinding after use. The process has a few steps, but isn't overly complicated for the aspiring photographer.
The basic idea is to use an empty cartridge, with either regular 35mm film, or unperforated film if you prefer to not see the sprocket holes. Use this film to reload into the cartridge, preferably a 24exp roll so you do not overfill the 126 cartridge. You have to do this in a light tight bag or dark room so you do not expose the film.
Some guides can be found here: