Use Browning Invector (not Browning Invector Plus), Mossberg Accu-Choke for the Mossberg 500 (not the Mossberg Accu-Mag for the Mossberg 835) or Winchester/Weatherby.
These all work.
Often times, these chokes will be advertized as "Fits Browning/Mossberg/Winchester/Weatherby."
The standard Franchi, Beretta, Benelli choke tubes do not fit the Stoeger.
You can get choke tubes through Benelli/Stoeger, but I think they're a little more expensive than just going to your local sporting goods store and asking for Browning Invector tubes.