One of the smallest wacom bamboo models is more than enough if all you want it for is osu-reasons. There must be cheaper brands than wacom too out there, but they're also more unreliable. Also I never really cared for the pen tips, I use my tablet for both playing osu (although I never touch with the tip while playing unless by accident) and drawing / working and in a year I never had to change it. My tablet came with 2 or 3 spare tips if I recall.
edit: Oh didn't read all you said now that I noticed. A A6 size must be okay for drawing too, at least everytime I tried one it seemed decent.
edit: Oh didn't read all you said now that I noticed. A A6 size must be okay for drawing too, at least everytime I tried one it seemed decent.