I couldn't find a list of vendors that offer these in the Vault Dweller's Survival Guide. Online, I saw a YouTube video that lists Alexis in Vault 81 and the trader on the BoS's Prydwen airship. I just visited Alexis, but the ONLY shipment she offered was for Circuitry. And until I decide to join the BoS, getting aboard the Prydwen is out of the question.

Given just how necessary fiber optics are for doing things like Leading PA pieces and modding energy weapons, it seems that Bethesda has made it too scarce. About the ONLY Junk Item that I found that I can scrap to get ONE fiber optic is the Biometric scanner. And there's only so many Machinegun turrets that can be scrapped. Makes it real tough to grab enough to Lead all six pieces of a PA set.

Anyone know of other traders that offer Fiber Optic shipments?

A couple of things:

+Microscopes have fiber optics, though they do have a heavy carry weight to them (3 wg each). You can find microscopes in most hospitals, especially Medford. After a couple of in-game weeks, you can farm the hospital again. You can also pick up fiber optics from disarming lasers. The treasure room in Jamaica Plains has a boatload, though you may want to take out the laser turrets first. They're pretty accurate and deadly (there are 4, if memory serves).

+Shipments supplied by vendors is random, so you'll need to check in every few days to see what they offer. I've seen fiber optics offered before, but it's expensive, so be ready to trade/sell. Once you get it, I highly recommend you take advantage of the replication glitch.

Oddly enough, the only thing I've yet to see offered by vendors is shipment of wood. That's the commodity I want more than the rest.