Heating Help

outside boiler for snow melt

I have been asked to propose a snow melt system with a load of 350k btu to the front walkway of an office building.  The boiler for the facility does not have the extra capacity for the additional load.  The location of the boiler room is opposite of walkway and gas line is undersized.  However, a natural gas powered generator with an adequate gas line is located outside and adjacent the walkway.  My question is what boiler or enclosure for piping are available.  I found Hot Box on the internet but am curious what others have used living in a similar climate.