You can try websites like Project Gutenberg. It has a large collection of free e-books, including some science fiction romance ones. Many classic works in this genre might be available there.
I'm not sure where you can find 'Modisto science fiction'. It might be in some niche science - fiction bookstores if it's a book. Or if it's an online work, it could be on some independent science - fiction platforms.
You can often find free science fiction on some public library websites. Many libraries offer e - book versions of classic and contemporary science fiction works for free borrowing. Also, some independent authors post their science fiction stories on their personal blogs or websites for free reading to gain popularity.