Find cartoonish girls with porcelain skin and large eyes in futanari manga, which are Japanese comics and graphic novels. These girls are the kind you're likely familiar with from anime.
Look for a more realistic style in futanari produced in the West. You'll find a more traditional comic or artistic approach to the art, with longer, leaner females. Oftentimes, American and European artists classify their girls as "shemales" and put them in more heterosexual encounters.
Check out the next generation of futanari, which uses 3D models to create comics. While these border on realism, they bring in more of the exaggerated features of manga.
Ask the comic book store you frequent to special-order futanari for you. Many stores do not keep adult titles on hand, but they should have no problem helping you get it.
Be specific when you ask for futanari. If you know the publishing company or the artist involved, you will have an easier time finding what you want.
Get futanari manga at Japanese bookstores. Most will stock both original comics and translated editions.
Find European-style futanari comics in adult bookstores. The further from manga it is, the more likely it is to be distributed right alongside pornographic magazines.
Attend comic and anime conventions. Most will have an adult or erotic section in the showcase area featuring both large and small publishers. Conventions are a great way to see a wide variety of futanari in one spot, making them ideal for getting acquainted with new artists.
Keep your eye on futanari forums and blogs for English translations of rare and popular comics. You'll often find entire chapters posted with full scans of the pages.