Mellotronists

A friend of mine demonstrated tonight his "Sonar 5" computer-based music  
package which had an impressive sound, selection of musical instruments, and  
editing and mixing capability.  What was missing, were tron sounds. He said  he 
wanted to find the best samples and didn't know where to find them.  Any  
suggestions would be appreciated.  I am fairly computer illiterate, so try  to give 
me info in a simple fashion.  Fortunately he's not, so he should be  able to 
understand the info.
 
Thanks, Craig