AirPods 4 case lost, mistakenly removed device, now can't connect either order a replacement

I have lost my AirPod 4 case. And I have bought a non-authentic case up until now, and it worked. Today, I have clicked forget device since my AirPods were not working properly; they were lagging. Now it won't even connect to my phone. I wanted to buy a replacement, but then the device won't show up. Please help.