Sorry to sound like a smart aleck, but the LEAST you can do it actually describe what you've already tried on this phone to get ringtones you've wanted.

That said, you do have a microUSB connection on the side of the handset. Ideally you could simply cook up your own ringtones from MP3/WAV files on your PC and transfer them over via the USB cable. Audacity is a free program you could use to make your own ringtones for free. The only question is, does the Sprint carrier software/ROM block such data transfer via USB(?) If you want info on this, head over to Howardforums.com and ask in the Sprint forum there for your options.