There are quite a few work-for-hire studios around although typically they assist rather than build whole cloth. Most others are working on their own stuff and trying to get funding rather than wanting to be paid to make other people’s ideas.

My suggestion would be to find and hire someone relatively senior with experience setting up game teams. There’s a bunch of Discords out there as well as some industry trade websites that host hiring ads. LinkedIn is a good bet as well and for what you want to do working with a recruiter that specialises in game jobs is probably a good bet as well.

In general people with an idea but no experience are treated with quite a bit of skepticism even if they have a budget! Getting someone with good experience on board to lead things will go a long way to help with that.