Herichthys cyanoguttatus is the only "texas cichlid", it is found in ranges from southern texas to mexico, the
Herichthys carpintis or "green texas" is found in mexico, its only called the green texas because (aside) from the color looks almost identical in terms of body shape. as for availability, im not sure where you live but my loca lwalmart recently started selling misc.south american cichlids and i often spotted texas cichlids in those tanks! or you can go here
www.liveaquaria.com
www.thatpetplace.com
they get very mean btw, my last texas grew a foot long so i called him hot dog
asfor thered texas, that wouldnt be considered a member of the Herichthys genus b/c of its man made b/r,sorry im rambling