I don't think that they ever offere the mirror separate from the base, & the p/n would relate to the whole unit (download the FREE Porsche 914 PET Parts manual at Porsche > Classic > Documents).
So you probably will want to modify your ad to find a complete unit, & you can try Bruce Stone/bdstone on here, HPH in Redwood City CA, & other members classifieds on here, evil-bay, TheSamba, etc.
You can also get them new from Porsche or any of their vendors (smae as used on 911/912/930 of that era).
You'll also want to get a couple of the 3M double-stick mounting pads - so you have a spare in the glovebox), which are $5-10 each & still sold by Porsche, dealers, vendors, etc. (also same as 911 etc.).
PS - The mirror is essentially the same for all 914 MYs & on all 911/912/912E/930 up to the late `80's or so, even if shown with different p/n's relating to those models.
Good Luck!
Tom
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