Basically your best choice is Cherry or BSP keycaps as they are the most easy to find PBT with 1.5 modifiers size. Cherry also have 6x spacebar, but I am still not sure what iOne uses for stem spacing on theirs and how much it will match up. Can always epoxy in some other stem if you are inclined. Like this
3000, have nice thick PBT keycap. Then you could get the 1x Win, menu and 6x space from a
7000 like this, look for cheaper price on one though, I did not look much just giving example.