If you can't find one on gunbroker, you might be out of luck. I seem to recall that Ruger was one of those companies that will not sell parts to their weapons, and they require you to send it to them for any gunsmithing. I am not sure if they still have hammers on hand for a Six gun.
And I think the sports car analogy is a bit off. Some guys have experienced a cracked forcing cone with relatively few rounds, while others have gotten thousands of rounds with no problems. So it's hit or miss.
If you go for a 65 (and they are a great gun), stick to 158 grain .357 and limit the use to maybe 10% of your shooting. Keep the fps to around 1100 and keep that forcing cone clean. I'm sure the gun will be fine.