You can pick up the yellow (amber) LED's at your local PepBoys automotive, It's LED194 on the package.... also available at Autozone and other toy stores. I think they were $15 for a set... available in red too (rear sidemarkers).
thanks! i use headlight covers and they dull the original bulbs back a bit so i wanted something brighter and maybe a different color(s) for a change - im assuming the led's are brighter