I bought an ignition switch for my TO-35 from AGCO (180681M93) but it has a plastic head key. Does anyone sell an original style switch and key?
Yes, AGCO began supplying these original switches with the later style key used on the later MF models. You can still purchase the flat metal key from AGCO as a separate part or you can purchase an after-market version.
Cole Hersee, who supplied the original switches to Ferguson and then Massey Ferguson no longer has this switch in their product line as a stock item but will produce them on a special order basis with minimum quantities of around 100 pieces or so.
There is an after-market version of the switch being sold by after-market suppliers which is ok, but slightly different than the original. Many people cannot tell the difference.