Yes these items are stocked from sizes ranging from less then 1/2″ to 2″ radiator valves and “steam fittings”
Before you start looking in your yellow pages you should know if your using a hot water or steam system.
The steam fittings can be used on either BUT the valves do make a big difference.
If your using steam heating it would also be a great idea to know your actual working pressure as we have systems here that work between 1/2 PSI to over 125# steam supply.
I am sure most local licensed plumbers in your area could be more then qualified to take care of your heating requirements.