I was able to get 181.fm custom channels to work. I went to shoutcast and looked for radio stations to use. Some of the http: links on shoutcast do not work some do. You just have to check different stations. All of 181.fm channels works using this method.
Go back to that station you want to listen to. Click on it and it will give you a download for your media player. I use VLC but I am not sure if windows media player will work the same. It will open and you will start to hear the stream you just downloaded. For the purpose of this tutorial I used the first channel which is 181.fm Awesome 80's
Once it is open right click on the name of the channel if using VLC and click on stream. The only thing you should be concerned with is the 4 digit code at the end. Copy it. It is 8000.
Go back to the live stream file and look for the line you added earlier and change the 4 digit number right behind 181.fm:. It should now look like this:
Save the file, start the game and click on radio and go to the bottom and click your station. You should now hear the custom radio ingame. Note you can also make changes to the file while the game is running. You just need to close then reopen the radio panel and what you just put in should be there.
Shoutcasts seems to have the majority of stations what will work in game so you should be able to find a station of music that you like from there. I hope that this helps you.