Not available to the public but you can buy one from Brownells???
It sounds like someone at Ruger service is having a bad day....
I have bought parts from Ruger many times and always have gotten the part I needed and service with a smile.
That said, The new Flat Top has a reverse indexing pawl and when the loading gate is opened the cylinder pawl drops completely out of the cylinder window,unlike the regular Blackhawk where the end of the pawl is still in the window when the gate is open. I have no idea if the pawls are different or not but there is something different that makes them operate differently. Your search to make sure you have the proper part is a GOOD idea.
Good luck!! Chuck