Hey there, I have been looking all over the internet for any music scores from Disney's The Great Mouse Detective soundtrack! No one seems to have copies nor does it seem to be available anywhere. Just wondering if anyone out there is lucky enough to own it, or know where I could find/purchase it?
You're just looking for the Varese Sarabande soundtrack CD? While I'm sure it's technically out of print, you can get it secondhand through a number of sellers on both Amazon and eBay. Here's Amazon's listing: www.amazon.com/Adventures-Great-Mouse-Detective/dp/B000008CPT/
If you'd rather have a digital copy, you can get it at the Amazon MP3 store, iTunes, etc.
Piano versions of "Goodbye So Soon" and "World's Greatest Criminal Mind" were reproduced in the 2nd Edition (and possibly ONLY that edition) of the "Disney Fake Book," while I believe the theme appears in "The New Henry Mancini Songbook." If these would be of any use to you, they seem to be easier to find for sale -- and you might even check with your local library to see if they can obtain them on your behalf.
If you're looking for something orchestral in nature, there is a concert arrangement available for rental through the Joann Kane Music Service, though I don't know how much that would set you back: