Can try House of Hung/Poh Heng range, if you're not fussy about diamond quality can try to buy from diamond warehouse / loose diamond sale (I checked at Michael Trio's online diamond list) I think you can get 0.4 ct for 1.5k? Then remaining 600 or so for ring setting.
Do note that all the 'online inventory list' are actually diamonds from all around the world where all suppliers have the access to the same list, and i understand that Jann Paul does offer you a lower pricing in the event you found certain online diamond from any other vendor and would like JP to bring it over for you instead at the lower pricing than any other online vendors.

