No, I don't have a source for large Haits. Gage usually has 3"ers. And he said he'd try to sex them for me if I wanted a male.
The reason is that they aren't wild caught and imported anymore. So you only have breeding pairs, and people only sell the offspring. And nobody wants to ever get rid of larger haits since they take so long and so much work to grow them. Plus, with the bloat issues these have, if someone takes that much work to raise them, they don't get rid of them later on down the road.
The last largish Hait I saw for sale was for something like $300 at 14" I think. Better off to just get some 3"ers, and grow out in that case, but it's going to take years. Large Haits seem to be super expensive.....
BTW, your Argentea was what made me start looking into them. Is that one of the Rio Tulijo's from Gage? It's really nice that you can get 7-8"ers for like $60, and they are gorgeous.