Door Air Cyllinders

["Olenick, Jamison" <Olenick@ssims.nci.nih.gov>]

   Has anyone been able to find a suitable replacement for the door cyllinders?
Or do they just rebuild them (if so then how and with what parts)?
   I found a catalog (I think Grainger or something of the sort)  that carried a
cyllinder that looked like it would work (for ~$60).  Will they?  

                                        Thanks, 
                                                        Jamie