I ordered one from here, if anyone else is looking: https://www.aliexpress.com/item/STM32F103C8T6-ARM-STM32-Minimum-System-Development-Board-Module-For-arduino/

I ordered one from here, if anyone else is looking: https://www.aliexpress.com/item/STM32F103C8T6-ARM-STM32-Minimum-System-Development-Board-Module-For-arduino/32811501377.html https://www.aliexpress.com/item/STM32F103C8T6-ARM-STM32-Mini... I can't vouch for the product or the seller, but for $2 shipped, the price is right.