You need to measure the existing top link at it's shortest length and at it longest length and get a TL that cloesly matches those measurements. I doubt you will find an exact match but get as close as you can.
See if CCM has any HTL's with check valves as these are the ones to buy if they are in stock. Otherwise you can get a 20"-28" one from Bare-Co or Agri-Supply. Agri-Supply will be about $30 cheaper for the same cylinder.