Thanks guys,

Stephen, I would suggest you buy them from Greg here:

http://www.rtbb.com.au/catalog/advanced_search_result.php?keywords=yellow+bulb&x=6&y=7

I had to do a big order from Marcos to get a few plastics I needed and the soccer ball motor controller board so grabbed what I needed in one big order, but I usually buy my parts locally, Greg is a top bloke who will be happy to help you out.