I know they're a junk brand but on ebay they have cheap sets you could just use the rears from or if you contact the company that makes your suspension they might sell you individually what components you need to repair it.
I've been running rev9 hypersteet2 on my cooper for over 2yr now 0 issues and they were very well priced. Actually my buddy got his Megan coilovers the same time for his r53 and we had them side by side and other than the green color being abit different, there was pretty much no difference and they're ride quality is the exact same , though mine have much less corrosion because my cars a garage queen but still, I'd have expected more corrosion than what's on them by now. They're threads are perfect still snd adjust very easily still.
I know it's an r56 but they still make them fir that model too.

 

What are you searching for? Just a shock is only $66/ side

Do you know what failed on the rear?

https://www.ecstuning.com/b-bilstein...19-215990~bil/

edit: It looks like you lost your main bolt that holds the bottom of the rear strut to the control arm, can you get a new bolt and refit ur suspension?

 

Still looking for the rear I got rear set for sale