Those look to be aftermarket mirrors of what brand, I'm not sure.
All 914s 70-76 had the chrome "Flag" mirrors, with the early cars having a sharp 90 degree arm, & later having a rounder 90 degree bend - which are the type for your 75.
Porsche still sells them new, & AFAIK they still even have new pass. side ones with a slight convex mirror (hard to tell the difference from flat because it's slight), & last I saw they were in the $230-250 per side range - less any PCA discount at P-dealers (or try at Suncoast Porsche & Sunset Porsche online parts depts. for best pricing), or from Jonathan at GPR, AA, Automotion/Eklers, Sierra Madre Collection is doing a 10% now for the Porsche Lit/Swap this weekend, or TC'sGarage will do 10-15% for PCA members IIRC (all are online).
You'll want new base seals from Porsche or 914Rubber, & mirror base SS screws are available at GoWesty.com (same screw on Vans as 914s), & maybe some other sources.
If that's too steep, then look on here, 914club, CL, evil-bay, TheSamba.com , etc. for used ones. Bruce Stone/bdstone & other members may have them. They usually polish up nice if not too far gone, & AutoAtlanta sells new mirror glass & seals for the late style ones, & maybe 914Rubber/Mikey914 on here &/or other vendors.
PS - For the used option (or new), you can use the L/driver side mirror flipped upside down on the R/pass. side, rather than trying to find a used R/pass. convex one. However, if you're popping for a new one, then you might as well get L & R new since the prices are the same (or close).
Good Luck!
Tom
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