Is there any where to get a small spray can of touch up paint in the GM color of my truck? (pewter)

My fuel door is starting to rust in the lower middle area of the door from water getting trapped on the inside wrap around seam area of the fuel door. I'm want to sandblast the door, bondo, prime it then paint it.

Paintscratch.com.
Not as cheap as Duplicolor but available in two step - clear coat and comes out excellent.

take your paint code into a auto body supply shop and have them mix up a can for you.