You know what? I honestly don't think I've seen one yet... One of my fics has very passing mentions of them but I truly don't know of any others that exist.

Sorry!

Have you tried ga_fanfic? I'm pretty sure there isn't anything there but you could double check... Hang on... I'll check for you... two seconds...

Oh, and do you mean April/Jackson as a couple, or just fics that feature them? Because there are definitely fics that feature them that I could point you in the direction of...

ETA: I just checked ga_fanfic and I was right, there is nothing April/Jackson over there... (not that is shippy anyway).