Need to add radiator to bedroom

I have an old victorian home that was originally steam, but is currently set up as a hot water boiler system.  I have a bedroom on 2nd floor that does not have any heat.  I'm not sure why since the other bedrooms do on 2nd floor.  The bedroom below on 1st floor has a radiator that could be tee'd off from to pipe up to 2nd floor.  I think it had a wood stove that went into the chimney access?

My question, is who should I call to have the radiator installed.  Would it be a Boiler service company, or a plumber?  I'd prefer someone who could help me size the proper radiator for the room.  I'm south of Chicago in Crete, IL.