Do you know of any schools or other non-profits that use ball-point pens, Sharpies, or even fountain pens?
It's a two part process: first, send a box of pens to an organization that needs them; second, send an email, letter, tweet, etc. to President Obama telling him that you donated those pens in his name.
While the word, "Veto" would not have to be used in your message, it wouldn't hurt. And it wouldn't hurt to include a mention of your support for the 'power of the pen' when yielded by this President.
To avoid driving the Secret Service nuts, it would be best to avoid sending any physical pens to the White House. It would also be best to avoid giving crayons. (Although if you have an old box of Crayolas that still has a pinkish/beige crayon labeled "Flesh" - it would be OK to send that to a prominent conservative.)
best,
john