Are there symbols for newer Windows key icons?

You could use the ⊞ ⊞ 'squared plus' symbol, which is basically four boxes, which is in essence a window, which should remain iconic throughout time, regardless of various stylistic changes. That is the character that Wikipedia uses for their Windows key article. In my opinion simpler is better in general, and for publications/documentation it should be easy enough to read/reproduce.

⊞ Win
SQUARED PLUS
U+229E, ⊞
LaTeX: \boxplus

It is a Unicode character, so I assume using a Unicode font would work for the documentation, however it is not part of ASCII, otherwise the # 'number sign' symbol is probably your best bet (which is the symbol AutoHotkey uses) to represent the Windows key.

Towards the end of the Computer keyboard article, there are links to other keys with symbols. For example, here some other 'special' keyboard key symbol/icon characters: ≣ Menu or ≡ Menu, ⌥ Option, ⌘ Command, etc.

edit: another suggestion would be the ❖ ❖ 'black diamond minus white x' symbol

❖ Win
BLACK DIAMOND MINUS WHITE X
U+2756, ❖

which would be more of a diagonal filled looking window, which might look more like the Windows XP logo than current Windows logo e.g. ❖ Win vs ⊞ Win

Try doing a capital W in the Marlett font. Success!

Because the logo is part of Microsoft's intellectual property, you probably won't be able to find a legit 3rd party font that includes it.

I think your best bet will be to create your own font with the symbols you want, being sure to be aware of whatever trademark notices you have to display if it includes 3rd party logos. It's probably a lot of overhead for what you want to do, so you'll have to decide if the time-investment is worth the use-value you get.