Savage Systems makes some. I have some...nothing special. They don't glow that brightly AND they are a pretty soft plastic. Not rigid enough for a nock in my opinion. They are out of stock on their website:
http://www.savagearchery.com/store.php?search[terms]=nocks&search[mode]=any&x=0&y=0
But, if you do an internet search for Savage Glow Nocks, there are a few places that have them:
http://www.outdoorsuperstore.com/product.asp?prod=527478&gdftrk=gdfV2348_a_7c40 4_a_7c1148_a_7c527478
Savage also makes glow vanes out of the same material.