This is a circuit design idea which uses modern SMPS (switch mode power supply) and a 9 volt (rechargeable) battery to produce 90 volt DC.
This is the traditional valve HT voltage utilized in the old 'portable' battery operated portable valve radio's of the 1940 - 50's.
I feel these batteries are now not manufactured (not even in China !).
They were always horrendously expensive, with a surprisingly short life.
One battery operated type which I once owned was always powered by a AC mains derived battery-eliminator.
However with modern high capacity ni-cad and Ni-MHd rechargable cells creation of an authentic looking "substitute" is possible.
See diag' which shows circuitry encased in a 'recycled' Eveready B battery cardboard outer casing.
Transformer ratio needs to be 1:15 to get correct o/p from a 9 volt battery.
Using a ferrite potcore or similar turns should be 220tns secondary, 2 x 15 tns primary.
The TL494 IC and most other components can be salvaged from disgarded PC tower smps (switch mode power supply) units.