This doesn't fit most of your critieria ("handwriting" being the most obvious, but also textbook storage), but it's what I've used and it works great for me.
iPhone (or any smartphone)
Bluetooth keyboard (I use Apple's)
Evernote
Evernote automatically uploads content to its cloud so you can edit and use from your computer without having to sync.
All you have to buy/carry in your purse is the keyboard - I'd chose a usable one that's a bit larger, like the Apple, rather than a small one that's harder to type on, since the main point will be to type notes quickly. Apple's keyboard is $70 or so, but compared to buying a barely usable netbook, I think it's worth it. Batteries in the kb last forever.
You could use a tablet instead but I find the iPhone screen big enough to read what I'm typing, which is enough.
Another benefit of the phone, is less temptation to multi-task.
Personally, I put the keyboard about a foot in front of me, with the phone in between me and the keyboard - easier to see, works better for touch-typing, less distracting to others I'm listening to.
I dislike handwritten notes, because they're barely legible and non-searchable.