It's been a while, but you can try Lavanderia Manfredi: Lavanderia Manfredi

Their website has a pricelist that includes wash/dry/fold services by the kg. But contact them in advance to make sure. Their website looks like it's from, well, the last time I would have been there (which is not in the past decade).

You can also try calling Lavanderia Il Giglio - it's over by the municipal offices on the eastern edge of the historic center. No website, gotta call.

Again, don't rely on any of this without calling. It's potentially dated info - these places still seem to exist, but that's all I can tell you. Hopefully it's a start.