The standard solution at the time was to use the transformer
from a junked valve television set or other equipment
(although the cheap table radios in the US often didn't
have transformers - they rectified the mains voltage for
the B+, and wired tubes in series across the mains - this
required an insulated cabinet for safety, and is less of
a good idea with 220V mains than our lower voltage!)
This project shows an example power supply, with the three
tube filaments connected across the mains, along with a
series resistor, although the B+ may need to be dropped
in your case.
If you can find a transformer that delivers a reasonable
lower voltage, then I've seen designs using a diode
voltage multiplier from that winding to get the B+.
You might have to wire the two valve filaments in
series to run on 12.6V, or use a switching DC/DC
converter (the valves will run on DC rather than AC).
Back when the unit was manufactured, some
receivers had a power jack on the back to allow
the internal power supply voltages to be used for
other projects. My old Heathkit AR-3 had one.
So a general approach these days is to see what
you can find for a transformer, and design the power
supply around that. I can often find plug-in AC
transformers at 16V or 24V that are designed to power
older alarm or telephone systems, like
this one.
You can then use a diode multiplier as needed to get
your B+, and a dropping resistor or regulator to get
the filament voltage. If you find one with 10V center
tapped, you can use half the winding for the filament.
If you can find a suitable transformer with a 6V winding
for the filaments, you can use an American unit with a
120VAC primary in reverse to step the 6.3VAC back up
for your B+.
And, depending on the transformer style, you may be
able to remove the secondary windings and add your own.
That's probably most practical if the secondary has a high
enough voltage that you can just remove turns, then add
another secondary (with fewer turns) for the filaments.