Seems like you can get PString from PString | Arduiniana. Extract the ZIP file in the lib/ folder. And Streaming.h from GitHub - geneReeves/ArduinoStreaming: Arduino Streaming Library (from Mikal Hart's site http://arduiniana.org/libraries/streaming/.
EDIT: The Streaming.h (or, Streaming5 library) is also available at https://platformio.org/lib/show/560/Streaming, as was recently discussed in Pio ci build suddenly fails - can no longer find library - #3 by maxgerhardt.