What is the term for a DC-AC Isolated Power supply?
It will probably be easier to find a suitable isolated DC-DC converter than a DC-AC type if you want to supply tube heaters.  

An isolated DC-DC converter has no electrical connection between the input and output sides, so you can bias each heater supply to suit the tube's cathode voltage.  

A non-isolated converter has a direct connection between the input and output grounds so would not be suitable for this application.