Modern Vespa

Looking to upgrade the stock Fly mirrors for some chrome mirrors, anybody have any good recommendations with part numbers? i see many different mirrors out there but just not sure which ones will fit. Thanks in advance

Mirrors, and the piece of the bike they screw into called the "perch," are all designed with a thread diameter of 8mm or 10mm, and a thread direction of "standard" (righty-tighty, lefty-loosy) or "reverse" (righty-loosy).

You would think the science behind the ideal thread directions would have been figured out and standardized eons ago, but nope, there is no standard. My S150 of similar vintage to your Fly has 10mm standard direction threads on both perches. If I had to bet I would guess your Fly does too, but I understand the current 150s have reverse threads on the right perch.

If you start with a set of these, for $7:
https://www.amazon.com/Motorcycle-Adapter-Standarad-Reverse-Threads/dp/B0CRGRG25Y/

then any set of 10mm diameter mirrors will fit any bike.

The stalk length and mirror shape are up to the rider and are highly subjective. They have a big effect on the look of the bike from the front, and of course define what you look at behind the bike, and how wide the front of the bike actually is for those who filter or are tight on garage space. I like longer 10" stems a lot more than shorter stems because a couple of inches has a huge effect on the rearward view.

Be forewarned that cheap chrome finishes rust and flake off very easily. I haven't found a huge variation in the quality of the actual mirror.