Perhaps we could start here:
http://www.turbosquid.com/FullPrevie....cfm/ID/477584
or here:
http://armada2.filefront.com/file/Sp..._Yamato;114523
The first one is apparently public domain and royalty free. I'm sure the author of the second could be contacted to request permission to use his model.
I hope this could be done.
Tigershark
Reading further, the author of the second model listed says in his readme that the model can be used or converted any way desired as long as he's given credit.