yup....go to gunbroker and type in this seller's name in the search box: lbf. That's Larry Friedman and he usually has a couple of subgauge barrels for Perazzi 12 gauge frames on his auction listings. The 20 and 28 are the most common I have seen, I have yet to see a .410 barrel for a 12 gauge frame but they do make them.
Just be sure to get the correct forend, e.g. a 28 gauge barrel with the 28 gauge forend fitted to a 12 gauge receiver, otherwise there will be a gap between the barrel and forend.