ATM corrector lens

[Bakernv@aol.com]

Hello all,
  I have a Criterion 4000 SCT spotting scope that is in perfect condition 
other than the fact that it is missing the corrector. My plan is to give this 
little scope to my parents for casual observing. (they know very little about 
astronomy) My question is what would be a good and affordable substitute for 
the original corrector yet still give acceptable views at low power? My dad 
will more than likely use the scope more often to check on his cattle herd 
than the stars. argh!!! Thank you all. 
Ron