I’ve been thinking about writing aids. I write very seldom because it’s often hard to control the pen, and therefore slow and shaky and laborious. I waste a lot of paper when my capital letters go wavering across it like dismayed stick figures. And yet when my speech or my voice goes, that’s what I’m left with. (Yes, I do have an AlphaSmart, but it’s not something I can carry around just in case, and this happens so rarely.) There’s nothing as portable as a pen or pencil, if you’re able to use them.
I do carry an alphabet with me at all times — that is, I can fingerspell, though more slowly now than I’d like. The problem with that is most people can’t read it. It has worked a few times, though. If you think something like that would be useful, here’s a fingerspelling quiz with other links to learn the alphabet. If you literally want to carry an alphabet with you, you could print out a picture of a keyboard and point to the letters on it, or print out a table with common words on it. (I’m aware there are more expensive options out there, but the less expensive options tend to come to mind first. This goes for pretty much everything.)
But usually I find myself indicating pen and paper, with a very patient person reading over my shoulder. It’s inconvenient for both of us, at least in terms of the time it takes. I don’t know if any writing aids would stop the tremor or not, but the Evo Pen looks interesting. There are other possibilities on the ErgoCube site.