I've been looking and looking, but the best I can find is using a narrow keyboard with a separate number-pad only keyboard on the left. I'm in the US.
(It's better for your right shoulder to keep the mouse closer to your body like in the picture.)
I am indeed a right-handed user, which is why I want my mouse within reach on the right.
May be worth considering too, especially if you're looking for a good keyboard with eg magnetic switches vs shitty rubberdome
[1] https://www.posturite.co.uk/left-handed-mechanical-keyboard
(If I needed a numpad I would have it standing alone.. those are easy to find)
It's easier to adapt to than than putting the mouse in my left hand!
found this one as well, don't know the brand: https://www.bloodyusa.com/product.php?pid=11&id=166