[Chad Hauris]

Nuvistors I think came out in the early 60's and were not used in any portable radios that I know of. Nuvistors used an indirectly heated cathode and I think that even if you were to try and use one the filament current draw would be too much for long battery life...all battery portables used directly heated cathodes for maximum "A" battery life.
There were some stereo receivers/tuners that used Nuvistor FM RF front end stages (for better RF performance) along with regular tubes or transistors for the rest of the unit.

The car radios of the mid-late 50's to early 60's used the 12 volt plate supply tubes as the transistors of the time could not measure up to the RF performance of tubes...a single transistor was usually used for audio output with the rest tubes. I guess the plate current demands would have been too much to try and make a 12-volt plate supply power output tube.