There are lots of extenders for 1 1/8" steerers, but not for 1".
You can use this 22.2mm quill to 1" threadless adapter though:

https://www.ebay.com/itm/374414170702

The only caveat is that you won't have a way to tension using the tension cap. You just have to push down very hard while tightening the quill bolt. If you really must tension with the tension cap, you can use a 1" BMX seat clamp:

https://www.porkchopbmx.com/mid-scho...-1-silver.html
together with stem spacers and a tension cap, to tension the headset first. Then you tighten down the 1" clamp to lock it in place. And then you use the 22.2mm to 1" threadless adapter.