Do you think those will ever be available over the counter?
I expect that like armor piercing rounds, they'll most likely remain very special purpose. The best bet for an individual who has use for 'em but isn't getting them as a line-of-duty use item will probably be to get them from someone who does.
In my case, trying to buy them from me wouldn't work, but a swap for a pizza dinner, or as an included magazine full with a weapons purchase might.