Hi,
Talk to bert or artnet...they have the used and new ones.
Go for a 10 inch, it will be much better than an 8 inch. You may say you want something simple and that beginner level dont matter, but you will be suprised at how fast your expectation rises..... :) alot of us have been through this process. Its not a matter of getting something cheap and that will do, its to get value for your money for something that you feel will last you for a considerable amt of time.
:D