You mean popular and classic songs? Look at karaoke-version.com. There you can make individual backing tracks, even for each instrument as a single file. They come as mp3, but in high quality. Or go to any free midi-file site, and make your own with garageband or so.
I dont have the Aeros - can`t it use mp3? Converting / upscaling an mp3 to wav does not bring more quality - only a bigger file. But you can use many apps: Audacity, VLC Player and houndreds of other Converter Apps. Or put them to garageband end export as wav.