It’s the rabbit goo harness from Amazon. https://www.amazon.com/Rabbitgoo-Harness-Harnesses-Adjustable-Weather/dp/B07MZRKC7P.

I heard about it from someone else on Reddit. I just put it on him and let him get used to the harness in my house. After about 10 minutes he was playing like normal so I just gave him some treats and took him right outside! He had a blast!