Does anyone know if pelletized corn gluten exists now for weed
control purposes?

It certainly does. I use a brand called "Weed Prevention Plus", made
by Concern. It's granular and is applied easily with a hand
spreader. You can get it online at
http://www.victorpest.com/lawncare/weedprevention.htm

Best o' luck in your war of the weeds.

-Fleemo