You might consider using the power supply from an inverter powered microwave oven. They produce as much as 1400 watts at about 4000 Vdc. Although they rectify the line voltage to create the DC input to the primary of what amounts to a TV fly-back transformer on steroids, it's the current through the primary that matters. Some modification would be in order, including adding another diode and capacitor to change the voltage doubler to a tripler to get 6000V Vdc. The inverters are pretty efficient. The magnetrons are not.