Model M2 and M use the same springs, so you can get some from Unicomp or Clickykeyboards or wherever you please. Some people possess the necessary dexterity to successfully pull and seat a new spring without having to crack the case -- I certainly do not

Aside from the many plastic clasps you can see on the back of the keyboard, the M2 is surprisingly easy to break down. It's a bit of a pain to reassemble. Try to keep it upside down when you take it apart, so the springs don't fall out as soon as you crack the case.