one 3mm diameter round bar(steel), about 80mm length, i took one from my old cd-rom.

Spring size suggest 35x3.2x0.4mm, or you can take a spring from your ballpoint pens( some modification for the module if needed).

a TC-02 Hotend needed, you can find the product in below url:

https://www.aliexpress.com/item/32956141783.html