I am making a circuit where I need to float one part of the circuit with (-200V) I am using isolating amplifiers ISO124 to isolate that part of the circuit.

An image below should explain what I am trying to say.



The part in the orange box is isolated and floated to -200V (floating ground, FGND). The problem I am having is finding power supply for the op amps on the floatable side of the circuit. The parts outside the orange box can be floated easily with any +- 15V power supply. What do I do with the part inside the orange box?

I have researched a bit and found several DC-DC isolated power supplies, but I am not sure how to float them so that I can have 200+15 V and 200-15 V power supply for the opamps in the floatable region.

I guess what I am asking is if there is a isolating power supply device something like
this?

Where there are three terminals on the output side ( right) and I can float it to whatever I want. If not? what other choices do I have. I have seen many people using optocouplers and isolating amps, there has to be something people do to power opamps in the floating side.

I can use the DC-DC isolated power supplies, but I not only have to float the FGND, but also the rail voltages of the op-amps relative to FGND like so:



I want the rail voltages to be FGND+15V and FGND-15V and not, FGND+30V and FGND.