Does anyone know where I can buy some of these fish?
You have already mentioned one of the most convenient sources, i.e., AquaBid. Many ALAers keep this fish, so you might also try advertising in the classifieds section of this website or submitting a "Want" list to go in the next Trader issue. There are usually some of these available at the ALA Convention auction which I believe is somewhere around Cleveland in the spring. As a last resort you might consider the Xiphophorus Stock Center (xiphophorus.org).
I didn't find these beautiful "Spiketail" platys very easy to breed, but as with any fish, conditions and results vary greatly. I have seen several different locations/populations available over the years. I believe the biggest differentiators are the markings, especially on the tail. One has a half crescent moon while another has a single dot at both the anterior and posterior base of the caudal. There are other variations as well, I believe.
Good luck with your acquisition. Let us know how your experience turns out.
"Former" Soapbox Speaker