Arduino Prototype to Finished Product
The route to go will probably be to design a custom pcb, it is almost certainly the most cost effective option. If you go down this route you will very likely need someone with experience in hardware design because there is very many things to consider here if you want to do it properly, especially since it is probably going to be a low power application?
Bare in mind also that true professional embedded programming (like stm32wb, nrf52, BGM or other Bluetooth MCUs) is nothing like programming an Arduino, so even this will be a project of its own with which you will probably have your hands full for months.
Good luck!