No, you only need an additional name server to serve one name, and it doesn't even have to be particularly reliable or fast or anything for most uses, as long a

No, you only need an additional name server to serve one name, and it doesn't even have to be particularly reliable or fast or anything for most uses, as long as it's available at some point for a cert renewal before the old cert expires. So, you can just put that nameserver on any machine that has a static IP address, or even a semi-static address, like, your home router or something.