Sorry to bump an old thread but it is the only one that I could find pertaining to the rear axle "Rear Aux Spring" GM PN
10386222 for my 2009 Saab 97x. I had one come off (dry rot?) during a rear brake R&R. Looked for this under jounce stop, bump stop, etc... and finally came across this thread. gmpartsgiant as mentioned above no longer has this part, nor does my local Chevy dealer. It is discontinued and can no longer be ordered by your GM dealer. I say this just as a warning to all that if you need them, you may find new old stock at your local dealer or online. It's probably a good idea to go ahead and get them if you plan to keep your truck long-term. Although I am sure there are substitutions that could be fitted if need be.
I should also mention that GM has dropped Saab from its parts database, so it makes it even harder to find the correct parts, even though 99% of the time it is the same part as a Trailblazer, Envoy, etc....