You could get it from a university library. There appear to be several ways to make it. First of all, this is a peptide, a short protein. Living things make these all the time, from amino acids. You could isolate the protein from a large mass of biomaterial -- harvesting a large number of these cone shells, and purifying away everything else. You could bio-engineer this molecule, by cloning the gene into a simple life form, and harvesting/purifying from that. One of your papers references this method. Short peptides, like this one, are also made on a protein synthesizers, using active amino acids, with Fmoc or Boc derivatives. And you have a reference to that process.
In either case, a peptide isn't made by adding functional groups to a carbon chain, as we generally do in organic chemistry, but instead one amino acid subunit is built upon another, one at a time.
There is also something functionally similar, but not a peptide, and you have a reference to that as well.