This is a peer-to-peer platform that uses Monero as its currency in order to protect financial privacy. It also has a non-custodial escrow system so that both buyer and seller are sure the money is actually there.
There was at one point a couple of years ago a system called Open Bazaar which I think could be forked and brought back to life that could do something like this.
They kind of made all the wrong mistakes though. First of all, it was just too early for decentralized markets to really take off. Second of all, it was after the Bitcoin block size wars and they chose Bitcoin anyway, and third, they used venture capital funding. I think if somebody redid it with Monero and community funding instead of venture capital, it might actually work.