I've noticed something...
Little Einsteins episodes from s1e01 through s2e12 were pretty easy to find. But after that, all the episodes have gotten very rare to find. You can find some of them in other languages, such as French, Spanish and even Arabic on YouTube among other places, but I can't find any of them in English.
List of missing episodes
13. Sleeping Bassoon
14. Rocket Soup
15. The Blue Footed Booby Bird Ballet
16. Little Red Rockethood
17. The Puzzle of the Sphinx
18. The Wild Goose Chase
19. Annie and the Beanstalk
20. The Wind Up Toy Prince
21. Mr. Penguin's Ice Cream Adventure
22. Annie Get Your Microphone
23. The Treasure Behind the Little Red Door: PARTIALLY FOUND
24. The Secret Mystery Prize
25. Animal Snack Time
26. The Great Schubert's Guessing Game
27. Quincy and the Instrument Dinosaurs
28. Build It, Rocket!
29. Melody and Me
30. Music Monsters
31. The Song of the Unicorn
32. Flight of the Instrument Fairies
33. Silly Sock Saves the Circus
34. Go Team!
35. The Music Robot from Outer Space
36. Show and Tell
37. Fire Truck Rocket!
38. Rocket the Bug
39. Little Elephant's Big Parade