Make your own.
All you have to do is connect the "sound out" on your computer to the input on a cassette deck, record the sound of the Utube clip, then use the recording to create your own WAV file. :D

here is a little tidbit of info. You don't need to record the sound on an external device and then import to the pc. You can use a sound editing software such as adobe audition to record the sound from the source right into a wav file on the pc.
I would definitely recommend Audacity. It is a freeware sound editing package and since getting it I have never had to look for audio software again!