What you need:

USB-C Charging Chip

2x 18650 Batteries

Switch
Motor

7x 20mm M3 Screw

7x M3 Nut

Links (affiliate):

Charing chip: https://www.aliexpress.com/item/1005004846748321.html?spm=a2g0o.order_list.order_list_main.132.22911802I0LoA4

Batteries: https://s.click.aliexpress.com/e/_opmBh7H

Switch: https://s.click.aliexpress.com/e/_oprQHUf

Motor: https://s.click.aliexpress.com/e/_oEZlUrh (any motor should work as long as the diameter is less than 20mm. I used a motor I got from an old car seat cover which had a vibrator in it)

Screws: https://s.click.aliexpress.com/e/_oC0LmSP