A long search comes to an end: HERE IS THE PRINCE OF TENNIS FANDUB
Here's how this went, guys: earlier today, my bro Ko from welcome datacomp found a guy with the file in question, one thought lost to time. I will credit him with his amazing Danbooru tag. As my router is currently torrent-averse, I put this up on Megaupload, but apparently it was already there. The file "uploaded" instantly. Well then, what we were looking for must have been under our noses the whole time. The treasure was always inside your heart! Without further ado, here's the fandub. If you want to stream it, here you go. Don't chicken out!