Bill at Eye Candy Coral sells them for sure. He always has them at the swaps. George I believe got one off of him back in MACI. I did see him with them at the swap either way.
Shipping is 12$ I think. At least to my area it is. Just add them to cart and put in zipcode for shipping price. I don't need 100$ worth of them either so I might end up paying for shipping.
There is a very easy DIY using a suregrip, any live rock and mortar. I've got a few on my back wall. Suregrips are not cheap, but it allows me to use my own light liverock and choose my shapes. I use BASF Emaco 400 mortar and Acryl 60 mixed up stiff. Use it to mortar the suregrip to the back of a rock. Wait 2 days and into the tank.
You can see one on the back wall right side. I don't have any more recent or better picts currently.