The thing is you don't even need to have a bigger keyboard: there is currently an input method that maps every key to a given kana. Not sure why it isn't more widespread though
The standard method of entering <ん> with either <n> or <nn> depending on context is silly, however, and I simply have it on the otherwise unused <l>.
Context is required to disambiguate ん vs an initial consonant of the な行. There's not really another choice unless you want to make <n> exclusively used for one or the other, which also isn't great.
<l> is also not unused, it's a prefix for the smaller version of characters e.g. <le> => ぇ or <ltu> => っ
Because the Japanese character does not depend on context, it is always <ん> and that one has to enter it differently depending on what follows it is annoying, especially when this can even be another word due to the lack of spaces. It is really counter intuitive to in that scheme to, say, type “一時間歩いた”.
> Context is required to disambiguate ん vs an initial consonant of the な行. There's not really another choice unless you want to make <n> exclusively used for one or the other, which also isn't great.
My other choice is simple; use <l> to input <ん> at all times since <l> isn't used in Japanese.
> <l> is also not unused, it's a prefix for the smaller version of characters e.g. <le> => ぇ or <ltu> => っ
That can also be done with <x>, which is the more popular version.