Tinkercad to design part (free, create an account to save your projects)
Good tutorial on Tinkercad, watch all six parts
https://www.youtube.com/watch?v=2JFxtUIOnEI
3D printer reviews in case you want to make it yourself
https://www.youtube.com/watch?v=UJyb-B4v7pk
Example of use (copying a part)
https://www.youtube.com/watch?v=ZJmkAngpRQg&t=68s
Online 3D printing service I’ve used, parts ready in about 2 weeks