Reddit mentions of Kuryakyn 8813 Splined Male Mount Peg Adapters for Front Footpegs and Floorboards: 1987-2018 Kawasaki Motorcycles, Chrome, 1 Pair

Ok, so here's the list, it's long.

Firstly, OEM parts:
Kawasaki LED Lightbar
Relay kit
12V Power Adapter
Passenger seat + frame and pegs.
Kawasaki large quick release windshield and brackets (expensive, but directs the wind higher than the puig windscreen, and I'm tall, so not many options. It's loud, and slight buffeting, but nothing too serious.)

All those can be found on kawasaki website, but shop around, as kawasaki prices are shit.

Third Party (some of these links may be sold out, but you can find them elsewhere too)

Kreiga Overlander OS-32 Drypack x2 - (Yes, the sell these individually, not paired. Yes, it's expensive. But holy hell, they are damn near bulletproof and absolutely 100% weatherproof!) I also use a 20 drypack for the top of the seat.

https://www.revzilla.com/motorcycle/kriega-overlander-s-os-32-drypack

Givi TS4115B Back Rest -
You'll want this if you get the givi luggage rack, really solid seat and rear rack. Pain in the ass to install, but worth all the swearing.

https://www.revzilla.com/motorcycle/givi-ts4115b-back-rest-kawasaki-vulcan-s-2015-2018

Givi PL4115 Side Case Racks -
These are what I use for my soft packs. It says they won't fit with trekker monokey cases but they do. The install obstructions (yes, I mean that) suck, they're grainy and black and white, and no, you don't need to move the turn signals. It requires removing a rear frame bolt and rebolting it while holding on to the fairing mount, the backrest, and the rack has been some of the most stressful moments of my bike's life. Prepare to swear. They are rock solid though, low form factor, and super happy with them. These need the passenger pegs to install, and should be installed at the same time as the backrest.

https://www.revzilla.com/motorcycle/givi-pl4115-side-case-racks-kawasaki-vulcan-s-2015-2019

Kreiga OS Straps -
Unless you buy the platforms (which are kind of ugly) for the racks, you'll need these to convert the drypacks into over seat bags. They sling over the top passenger seat, and tie down snug on the bottom bar of the rack. Super easy and you don't feel them as a passenger. These are sold as a pair.

https://www.revzilla.com/motorcycle/kriega-os-straps?rrec=true

R&G radiator guard - the radiator on the vulcan is super exposed and eats a lot of gravel. Definetly install a radiator guard if you plan on riding back roads. This does the trick, a bit pricey for my taste, but it looks nice.

https://www.revzilla.com/motorcycle/rg-aluminum-radiator-guard-kawasaki-vulcan-s-2015-2017?rrec=true

Kuryakyn Ribbed Folding Floorboards - best addition I've made to my bike. Makes long distances super comfy, and don't look out of place at all on the bike. Easy to install too. They don't scrape at all either if you corner properly and don't front load it. They do produce a strong vibration depending on where you place your heel, but I have thick soles on my boot and barely notice it even after a few hours. Would not feel good on tennis shoes though.

https://www.revzilla.com/motorcycle/kuryakyn-ribbed-folding-floorboards?gclid=EAIaIQobChMIhbSIm8TB4wIVCITICh315wXQEAQYASABEgIM2fD_BwE

Splined adapter for floorboards - You'll need this to install the floorboards. Revzilla part numbers are trash and don't match up. This is the adapter to fit the vulcan. It says it doesn't, but it 100% does.

https://www.amazon.com/Kuryakyn-8813-Front-Splined-Adapter/dp/B000IOJ496

Heated grips I'm aiming for are Oxford touring grips. They're the correct length, and will allow me to keep the oem bar ends.

https://www.oxfordaccessories.co.uk/products/kawasaki-vulcan-s-oxford-el691uk-touring-heated-grips-hotgrips-motorcycle-motorbike-bike-uk-spec

The vulcan s has a small alternator though, so I'll need to do some math to make sure I have enough headway. I may have to convert my turn signals and headlamp to leds to get enough room for them, we will see!

Was also going to add 2x fuel canisters in holders at some point, vulcan has a small tank, and I don't want to run out in the woods.

https://www.msrgear.com/msr-fuel-bottles

Gear:

Shoei RF-SR (Orange)

Scorpion Optima Jacket
https://www.revzilla.com/motorcycle/scorpion-optima-jacket

Fly Racing Street Terra Trek Pants
https://www.revzilla.com/motorcycle/fly-terra-trek-pants

Scorpion Divergent gloves
https://www.revzilla.com/motorcycle/scorpion-divergent-gloves

21 RPM Boots
https://www.revzilla.com/motorcycle/highway-21-rpm-boots

These keep me almost 100% waterproof (only thing that gets wet is my hands, those gloves are mesh top, and all of these vent really well even in 90 degree weather. The jacket and pants both come with thermal liners as well so they keep me cozy when the temperature drops too. Just change out the gloves if you want to be totally weatherproof, I just like a little airflow on my fingers.