WSS used to carry them, but as of late I have not seen them advertised online.
SKB made them a few years back under license for Weatherby.
There is one or was a late 70's in the EE section last week that looked pretty sharp.
I had to pass on it due to the fact one of my guns did not sell ;(
Another buddy had one he shot for a couple of years he then sold it after someone offered him what he paid for it even after shooting it for two years.
He now shoots a Citori 525 Sporting Clays iirc and he says they are very similar, but caught on with the Browning real fast.
Sorry , I can not speak to the chokes, but I am surely Briley will be able to handle your choke selection should you not like the factory.
Hopefully someone else will have more information for you.
Rob