MP5 F stock

I recently picked up an F style stock that has lost it's spring tension. I carefully took it apart as to not to loose any parts and noticed that the little cup that holds the spring has worn out. Even the lever has the hole where the spring goes wobled out a little. This is the first F style stock I have had a chance to get close to and was a little dissappointed that one of the main parts of this thing is of such poor quality. I got it at a decent price so I figured I take a chance on it.

Now to my question. Does anyone repair these things or know anyone that does?

I can't seem to find the parts I need on the net anywhere.