Looks like Hilversum is rediscovering it's heritage! People are actively rediscovering Walhalla Symfonie, and there are now some "official" releases online.The KRO has a website called "Uitgelicht" which publishes old programs - and you canpost requests! I asked for one of the Walhalla's I didn't have "And then they saw the Pyramids" and they found and posted it ;-)
More recently the late night program "De nacht van het goede leven" will transmit four Symfonies (announced here). You can listen to the shows here.