Did some more playing... the 429 error is coming from the plex server.
The good news is that I manually edited the us.m3u8 and appear to have a working solution (been playing for about an hour now after failing in about a minute).
- pointed the stream links to the plex server
- added X-Plex-Product=Plex%20Web
- added X-Plex-Session-Id=[new unique UUID]
- generated a new X-Plex-Client-Identifer=[new 23 char alpha-numeric string]
- generated a new X-Plex-Token=[need to generate from a Plex account]
It's the last one that I think really fixed things. Not sure how the token is currently being generated or if he's trying to use a static token.
cc @matthuisman
Guess I'll work on figuring out the correct encoding to try it out.