Well, reading the OP's post, it states a 40 times increase in resistance. A little bit of very gentle curvature is not the same thing. If the OP is seeing a 40 times increase in resistance, maybe there is some problem with the measurement. That is my point. Also, if anything the RDSon goes slightly down with smaller VDS, not up.
For enough money, I would. If the OP would even just post the full specifications required of the circuit, I might do it for fun. For no money, without the specification of what it is supposed to do, all I'll provide is my opinion, which you and the OP are free to ignore if that suits you best.