I can't remember the last time I saw a 40" range it is an odd size that does not work with most cabinets manufacturers sizes so that would be the reason I think.

Check ajmadison.com . Frigidaire and Ilve make 40" ranges.

40" is 1,000mm in Europe and a fairly common size there. We have 4 different models in this size (1, 2 or 3 ovens).

I think moving up to a 48" would require more work on the existing cabinetry. With a 36", you would only need to add a filler piece on either side (in an over-simplified scenario of course!). You could also keep your existing hood, whereas a 48" range would most likely require a new one.

Good luck!

Aga makes a 44 inch wide range.