Do you mean unheated/ untreated sapphires? If you are ok with heating, which many people are that will open your options to sapphires as the price is lower then unheated ones. If you want 100% natual, unheated/ untreated sapphires in that carat range it might be a stetch. You will probably have to sacrafice in color, cut or clarity.
Do you care what the shape is?
I would contact Dana at Master Cut Gems to see what he has. I think his sapphires are on the more affordable side. Forwarning that his pictures are nearly as good as the RL stones!
I don’t think you can get a nice looking unheated natural sapphire with a halo ring setting within a budget of $1300. I presume you are looking for a blue sapphire? If you are willing to do a heated natural sapphire or Beryllium diffused sapphire, you can get something very nice for under the dollar amount stated.
For the stone, check out Tan’s various stores such as Gemburionline, VVSgems and Odysseygems.
For the setting, check out Lanb08’s various eBay stores.