We have a six-unit triple decker apartment building in Cambridge, MA, USA. We installed Danfoss thermostatic radiator valves on each of our hot water gravity system radiators about 25 years ago. They are beginning to fail now after many years of service. The plumber is having difficulty fitting now-available radiator valves onto the existing pipes in this 1911 building because of differences in pipe sizes. We were wondering is there is some Danfoss radiator valve graveyard somewhere where we could locate a number of our valve type. We've had two fail already, with more sure to come along (36 total in the building). I could send a digital photo of the valve we're trying to match. Thanks ahead of time for any help.