Posted by: Rolly
Your looking for a device called an injector. I have not seen any made for steam above 300 PSI. Injectors have a reputation as being temper mantle but I believe its more operator error then the device. They need to be kept clean of debris and like cold water on the suction side.
I use a Penberthy 1/2 inch model AA-328 rated 50 to 200 PSI on my 35-foot steamboat Tryall.