[Arran]

Building a more permanent C- supply isn't too hard, the biggest issue is trying to remove the AC ripple from it but that's where voltage regulators can come in handy. The old fashioned way to supply C- was to take it out of the B- string with a series of resistors, but a cheap Pi filter network with a choke resistor won't cut it for battery sets. The one good feature with console battery sets is that they usually incorporated a shelf to store the A and B batteries, so there is lots of room even to put an all tube based battery eliminator/power supply let alone a SS one.
Regards
Arran