Seems like this could be an interesting niche for a fediverse project. The only option that seems to think in that direction that I could find is Epicyon.
Seems like an ideal application of the federated technology. Start small as a neighbourhood sharing/bartering network and over time it can expand easily to cover an entire city or such.
Probably not what you’re looking for, but Hubzilla has a
cartaddon that is an online store you can host in a channel. Documentation is scarce and it’s a tad on the primitive side, but useable enough for simple shops.