Most were dealer installed on the 914 4's - so look at Jeff Bowlsby's 914 website sections on Accessories & Options - then narrow down your choices to which you really want - mono, stereo, with 8-track or Cassette, then update your ad here.
Then search these classifieds.
Also, try doing a Google search for those already listed on here & elsewhere (the 914world search function doesn't work very well for that).
Good Luck!
Tom
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