These Field coil drivers are available with DC power supply which you should inquire with the seller,to be bought as a package or otherwise this power supply can be sourced as custom made from various tube amplifier designers around the globe, one of them is jeffrey jackson,USA and Thomas mayer from germany, but sourcing from outside will work out to be very expensive and it is better to source the same from speaker supplier.
For instance Lowther USA for their field coil drivers had recommended me to buy a HP laptop power supply as alternate cheaper option which could have been sourced locally in India also,and also conveniently available off the shelf.
While requesting for purchase,better you mention your plans whether you want to use them in Open Baffle or boxed enclosure,so if the manufacturer as different models for different implementation ,he will suggest accordingly
Cheers
