Your only answer, unless you are willing to settle for a 625 and even then the 4" versions are uncommon, is to find a 25-2 and have it cut down. I think a 45 ACP with a 5" barrel is ideal so I had one made:
In this case I found a less than collector grade Model of 1955 and had my gun smith cut it to 5". If not my favorite revolver it is in a tie with which ever one is the favorite. (smile)
Dave