The rear wheels are the same as used on the Monster S4S.
I brought one a while back off of ebay for around 200 quid including sprocket carrier.
FYI a new wheel from ducati without disc or sprocket carrier is about 500 quid !!
Once you get the wheel stick it in the bike without a tyre on it and spin it so you can check run-out, and see if it has any flat spots. This is the easiest way to quickly check its condition.
Mine was perfect.
Cheers,
John.