Below is a basic list of parts and websites I use when building game boys with tips on best practices. I know sometimes it is difficult to find things when you do not know what you need. These are quick Amazon links but some of these parts can be sourced elsewhere for cheaper (may take several weeks for shipping).
If you want to use standard buttons you can get them on amazon, or ebay but they’re expensive. I recommend going through handheld legend instead. They have two piece customizable buttons you can mix and match.
Amazon.com – Basic Board
You can attempt to get in on a preorder from http://www.sudomod.com, but the boards only come up for sale every few months and take between 2 and 4 months to get once you pay for them. They’re really convenient and save money. If you don’t have the patience, there’s a good common ground board on amazon I regularly use for 10 bucks that work great.
BUTTON CONTROLLER BOARD
Teensy LC USB Development Board Without Pins
If you don’t have an all in one, this board is what tells the raspberry pi what to do when your buttons are pressed. You can use various audrino compatible boards such as the teensey LC and audrino pro micro.
This is always a tough one for me. If I need a screen in a pinch, I’ll buy the Adaftuit 3.5 pal screen, although it’s quite steep at 45 bucks. You can order the BW screen from amazon, but it has many, many different controller boards that may need to be converted to 5V. I’ve even had some with the visually same controller board, that are different. I usually order this screen from gearbest, and it always has the same controller board that’s really straight forward to convert to 5V.
Tactile switch for L and R
I use these because I put mine through the back of the case. But you’ll want a slightly longer one if you’re going to go through the reat screw holes because it’s thicker.
There’s two different ones I use.
The adafruit powerboost 1000C : Interface Modules Rechargeable 5V Lipo USB Boost
The bangood which is sufficient to also power a pi3:
Targus 4-Port Hub, Black/Gray (ACH114US) You always need to be careful when buying a usb hub for the pi zero. The onboard IC can only handle one usb device, so you need a host USB hub that registers each device as a new usb device before sending it upstream to the pi. There’s a couple that work great, but I perfer the targus.