Okay, i have a girlfriend nagging me to play on my Sega Pico i bought today

Anyways, i seem to be missing the Flat Yellow piece that slots onto the bottom panel below where the book-carts go.
(im guessin its known as a sensor or something, basically where u use the pen...)

Is this piece vital, im guessing so as i couldnt seem to do anythink with the pen :/

Are there any place for replacement ones or possible a guide on how to make one?

Cheers