How do I make invisible ink?

Question

Real invisible ink that shows up under a UV light, not lemon juice/baking soda grape juice/milk heated up.

I need it in the colour yellow, and I need to make it or buy it (can't find yellow pen) within a few hours.

Really desperate here, is there anything that could be used as a substitute?

Answer 1

You may also buy the invisible ink from here
http://www.glowpaint.com.au
Tonic water will also fluoresce under UV light...