These are some parts and motors I've ordered. Not all have been vetted, but this provides a record of their source.
|n20 6v 500rpm||$1.97/ea||https://a.aliexpress.com/_mNLg48i|
|n20 6v 300rpm||$0.68/ea||https://a.aliexpress.com/_mP0aLKa|
|ChiHai 16mm 700rpm||$12.55/ea||https://a.aliexpress.com/_mLiNOYK|
|Emax 1104 4300kv||$1.70/ea||https://a.aliexpress.com/_mqh2Aie|
|20mm Planetary w/130 motor||$1.20/ea||https://a.aliexpress.com/_mtMWO6e|