problems with used motivational setup...need advice

[Marco Canta]

I just acquired a set of used motivational coil overs,
for a good price, but there is a problem with one rear
coil over.  The plastic threaded collar is damaged so
the adjustment perch is stuck at that height.

So my question is should I:
1) buy 1 new coiled strut by itself (reuse the spring)
2) buy 2 new coiled struts to match (the setup was
used for about a year)
3) buy 4 new coiled struts to really match (not
necessary?)
3) or maybe it's possible to send the damaged strut to
Motivational to fix the collar?

Thanks,
Marco