The post linked above in my first reply had screen shots and instructions telling you how to do this. Lets try describing it: You right click/press hold the taskbar and select "Show touch keyboard button" - you may have to exit tablet mode to do this. Touch the very last icon on the right to bring up action center and then touch tablet mode (it is a toggle). then you should be able to press and hold a blank space on the task bar as shown in the images in the post I linked.
You don't need to purchase anything.