Better check what the range maker suggests and also install with make-up air a 42” hood fan will cost a few$$$

I bought mine at Ferguson. There are showrooms across the country and online.

While the general wisdom is that the hood should be larger than the range, it's a little less of a concern with a wall-mounted installation. The wall and the surrounding cabinetry will help to direct the "air pollution" into the hood, unlike an island-mount installation that's open to every cross-draft.

It really comes down to your cooking habits. Are you making a dinner for a family of 6 every night? Then yes, you need a huge oversized hood. But if you're typically using only 1 or 2 burners, and don't get into anything extreme, you could get away with a hood that matches the range.

There are many more 36" hoods on the market than 42", so your selection is much wider.