You can get it on Amazon! I found it from /u/Spiritmetaphor post a little while back :)
Ye Olde Amazon: https://www.amazon.com/Hinterfeld-Aquarium-Crystal-Shrimp-Holder/dp/B015FN4LRE/ref=sr_1_5?ie=UTF8&qid=1512608890&sr=8-5&keywords=aquarium+plant+holder Need to provide your own moss ball.
I got mine here!