Raspberry Pi Zero boards are often in short supply, but the V 1.3 model is regularly on sale for around $5 from Adafruit in the US: https://www.adafruit.com/product/2885 , or for about £5 from The Pi Hut in the UK: https://thepihut.com/products/raspberry-pi-zero . Note that these are not affiliate links, and that I have no association with these companies.
The plastic sheet I used in this project is known as “plasticard”, and is sold on Amazon.com and Amazon.co.uk under this name in a variety of thicknesses.