Front Bumper Directional/Blinker light help?

[71 Blazer CST man]

When looking head on at the front of my blazer, my LEFt (so its right?) directional/blinker burns not nearly as bright as the other. This is very obvius to tell especially when my hazards are on Just wondering if any of you know why? I cleaned my lense, and chanced the bulb. I noticed only one of the filements(spelling?) in the bulb lights (Same as the old/dirty bulb) when on.....is this the wrong bulb? Are they both supposed to be lit? Havent pulled the one on the other side to see how it functions. Just wondering if any of you have a clue. Thanks. Oh and, on that note...where is the best place to by CLEAR lenses with orange bulbs...or any light needs in general for our trucks?