I agree with David Klass. He's work is lovely. Other options would be Victor Canera, Leon Mege (reputed to be difficult unless you cede all create control but hand-forges rings and has talent to spare), Steven Kirsch, and Maytal Hannah. It would be useful for you to narrow your wishes do you can get a quote from multiple vendors that are apples to apples. If your pear is as large at those latter two examples, I'd stick with a split shank (friction is your friend to help avoid spinning).
You shouldn't have a problem staying under your budget with the first setting you posted. Settings 2 and 3 could be questionable depending on the vendor.
You'll need to give them a call and send them some pics. They're usually happy to provide quotes if they are willing to do the setting.