Whirlpool Gold GR445LXMS - Fifth Burner Infinite Switch

Hello,

I have a Whirlpool Gold GR445LXMS electric stove. Every parts diagram I can find (including here) on this model shows only four burner elements, but we have five on ours (our fifth is a central rear 6", single element, keep warm function I believe).

I need a replacement infinite switch for this-can anyone point me in the right direction?

Thanks and regards.