There isn't any pygmy seahorses for sale. They are way to tiny and fragile. Pygmy seahorses are not even an inch full grown. They usually live on an host gorgonian. To keep the seahorses alive, you have to be able the gorgonian alive.
Now if you are looking at dwarf seahorses, these grow up to an inch and a half to two inches. There any many places that sell these.
Hippocampus barbiganti live on only 1 type of Gorgonian, which despite much success with several nps gorgonians I have never even remotely had any luck with, that gets to be huge. I've never even heard of public aquaria successfully keeping these.
Yes I have seen these teeny tiny seahorse living and camouflaged in gorgonians while diving in Indonesia. They are so tiny and fragile I can't imagine what it would take to keep them in a tank...... There are so many other species to explore including wonderful captive bred seahorses. Hopefully you can find wonderment with 1 of these other ponies....