Another idea which I have now used and is excellent is an ArtPad II It is available as Dos/Windows or Mac and it comprises of a “pen” and a “pad”. The pen you direct and hold as you would when writing and you click on the nib which can be a sensitive as you light. If you do alot of graphics it has an eraser and the right click button is on the pen which you can just touch using your thumb.
I have used it for a week now and it is great particularly for people like me who developed RSI in the knuckles and forefinger due to clicking on the button. It costs approx ?179.00 produced by Wacom