After a bit of trial and error I discovered that a Hot/Cold, usually blue, flexible medicine bottle is the best solution for me, for a pee bottle. I don't believe I've seen anyone made reference to using it for this purpose, but these are the benefits I've found:
Generous intake port - Not too much aim, or unnecessary precision required.
I don't think anyone would ever confuse it for a drinking bottle, even at night.
When you "filler up" you can use it as a heating pad, which will conform to what ever body part you place it on - That's originally what it was made for afterall!
It takes up very little space, by collapsing to a tiny ball.
And, of course, its lightweight; plus you can find them absolutely everywhere.
Works for me.