You can get the GTA 4 "Soviet Connection" theme and various in-game ringtones (zil sesleri) as MP3s through several sources.
: Detailed compilations of all purchasable in-game ringtones and sound effects are available on YouTube . Gta 4 Zil Sesi Mp3
If you are looking for specific in-game notification sounds or the ringtones Niko uses on his Whiz or Badger phones, you can find them here: You can get the GTA 4 "Soviet Connection"