Missing stylus/pen

Question

I recently brought a graphics tablet on ebay without seeing that the pen was missing, obviously my fault for not reading the description properly but that doesn't really help my problem. I need to know where I can get a repacement pen for the Nisis product I have brought, or if not a pen of the same make then a different stylus that will work on the tablet. Please help, I've looked everywhere. What can I do?