If you are handy with a soldering iron, here are a few url's to power supply circuits. The first is unregulated, but works well, and I ahve made quite a number of supplies based on the circuit, with some minor differences.
http://antiqueradio.org/bsupply.htm
There are also a few links to other pages in the site if you wish to make a vintage supply. The above circuit was adaptable to a supply that used a "BH" gas rectifier.
http://antiqueradio.org/art/cv1202.gif
http://antiqueradio.org/art/cv1201.gif
http://antiqueradio.org/art/bsupply01.gif
There are also some useful circuits at the California Radio Historical Society
A regulated "A" supply, http://antiqueradios.com/chrs/journal/asupply.html You may need to change a few values if you are using a radio that uses a 1.5, 2, or 3 volt "A" supply. To get lower voltages, you will need to alter some of the values in the circuit.
A regulated "B" supply http://antiqueradios.com/chrs/journal/bsupply.html This one is more sophisticated than the one above, but is more stable.
: I have a Canadian Stewart-Warner bakelite tombstone battery model R-521. Is there anywhere I can find a battery or a converter to get it to play?