This went down well at the ISTA conference in Letterkenny at the weekend where I was demonstrating as part of the Science on Stage team and I promised people I would let them know where I got it, so here it is:
teachersource.com

There is a lot more where this came from. I posted a brief note on the site recently , so browse the entire site. Remember the dollar has rarely been this low.

I will stick a video of the kit in action on youtube sometime this weekend (hopefully).