The likelyhood of these showing up on YouTube is low due to OtterFan25 (who had previously uploaded many of the show's credits instrumentals), getting two copyright strikes from Dan Saywer for his videos, meaning anybody who uploads these is at risk. However, a few videos from wrightgirl11 remain along with other users' uploads of episodes with credits at the end.
Credits instrumentals remain at large for 19 episodes and at least 6 of the found instrumentals cut off early.
Update 12/24/13: The credits instrumental for "The Dollhouse / The Tell-Tale Candy Wrapper" has been found! http://www.youtube.com/watch?v=hzvXefxUExM
Update 1/9/14: Disney Junior has put one of the missing credits instrumentals on demand for the episode "Gotta Dance / Otter Pox" and we can expect a MEGA mirror in the next few days!
Update 5/27/14: The credits for "Strike up the Band / World's Strongest Otter" has been found! http://www.youtube.com/watch?v=NRmYDeNJX2Q
Update 6/16/14: The credits for "A Tree Grows in Hoohaw / Flick's Big Fakeout" are available on Retro Junk!