Do you care if the plastic is on the outside? I’ve got a Morphy Richards one that is all metal except for the handle.

Edit: and also the little transparent bit where you see how much water is inside. Hard to make that out of plastic or wood. The electrical cable also contains plastic but that seems important.

Edit edit: Now that I think about it, a 100% metal electric kettle sounds terrifying.

Stove top kettle

There’s a nice breville one that only has plastic in the on switch. Body is glass and metal