Strava

I use topofusion to do something similar:

• Output SRM file (filename.srm)
  
• Open in Golden Cheetah
  
• Export ride data as CSV (filename.csv)
  
• Open the Garmin ride file (ride.tcx) in Topofusion
  
• Using the Power Analysis tab "add" the CSV to the file
  
• Save the new file as a TCX (newfile.tcx)
  
  

You should then have a file with everything from the Garmin and the SRM.