Cant seem to find a tablet where the wifi can be disabled permamently.
Wait a little bit longer for the Librem 11 tablet to be formally announced in the coming weeks from Purism, then preorder it if it meets your requirements. I suspect it will have hardware kill switches just like their other products.
If you are feeling particularly ambitious, consider disassembling mainstream consumer tablets yourself and see if you can accomplish your objective that way.
Or, for permanent disabling, if it will be like the Librem 5 then you can simply remove the WiFi card.
Or the Librem 14 and the rest of the older laptop models for that matter.