If those are 13cm (5")speakers like they are used in a Audi A3 or TT you could get any of these (for example the Bose or Harman Kardon ones
if you want to spend that much)
What about the mountings in the doors?
Also: If you are concerned about speakers being to deep (fitting in the width but not in the depth) - below the top cover of the dashboard is another one - if you cut a hole in this one - any speaker fitting concerning the width would fit in there.