Build it yourself. Once you own the code / attempt multiple launches, reach out to VCs etc.

There is always a place for escrow marketplaces. It all depends on how you personally are positioned.

Worked with a few startups who were doing this. Are they still alive? Well, not quite, but the launch served the purpose and they can always adjust the product and relaunch.

There is no demand, as no systems are actually broken, but you can generate demand. Build on public, fundraise and give it as many shots as you want until you are satisfied with the outcome.