[airbreather]

aliexpress is a goldmine, example of some small stuff with metal gears, very good manufacturing tolerances

https://www.aliexpress.com/item/1005004936458606.html

https://www.aliexpress.com/item/1005004830455177.html

https://www.aliexpress.com/item/4001110546573.html

[conductr]

As FYI, on many of these you can get on Amazon/Ebay. You'll pay a buck or two extra but get it the next day.