Some independent blogs or personal websites dedicated to Once Upon a Time might also host fanfictions. You can find these by doing a simple Google search. For example, search for 'Once Upon a Time fanfiction blog' and explore the results. But be careful as the quality and legality of the content on some of these sites might vary.
You can try fanfiction websites like Archive of Our Own (AO3) or FanFiction.net. These platforms have a vast collection of fanfictions from various fandoms, including those related to 'Once upon a time' and 'Watch the future'. Just use their search functions to look for the specific fanfictions you're interested in.
Sometimes, it's also available on cable TV channels that show family-friendly movies. Check your local listings. Or you could rent or buy it on digital platforms like iTunes or Google Play.