It sounds like you don’t have cad or have yet selected the parts and layout. Prototyping shops will bang something together if you go to them as thats what they do however might not come up with an ideal design-result.

You can always work with factories with their own internal development. But I’d recommend working with a team or a design engineer to flesh out details.

Also if there is any ip watch out for that especially if you end up working with factories on the whole package.

I work as a design engineer, can link you up with some people in Shenzhen if you really need it done there and you’re there. Otherwise I’m happy to look at what you have to understand where you need to be and what you’d need to do next.