Go to satwa or Deira Naif opp shingdaga tunnel and car accessories (especially iranian) fellows will show you many many options, whatever u like, Just CD, MP3, WMA, USB, IPOD, Nav no nav etc.
Make sure you bargain good and cross compare few shops in line so that you dont end up paying more than what its worth for. As these guys ask too much in begining like 1000 dhs and end up giving it same with installation in 400 dhs.