Could be .38 Long Colt, .38 Short Colt(not likely) or .38 New Police depending on what revolver.
Ten-X, Stateside, loads Long Colt. Don't know who or if you can get it here.
Reloading is the way to go. Long Colt brass can be made out of regular .38 Special brass by trimming to 1.031". Same case otherwise.
There are two loads using a 125 grain and 150 grain LRN with Unique or Bullseye on Handloads.com. Several loads for both bullet weights on Hodgdon's site. Lee makes dies.