we used to be able to find a 3M seam sealer locally. i'm sorry i don't have more detail, but its used to come in a white tube. 3M has a white and a black color, and the white is a really close match to what mazda used
oh that was easy, try this
http://3mcollision.com/3m-fast-n-fir...oreInfoDetails
i think we used to just get it at a paint store, and not the regular hardware store, but maybe the hardwarestore had it too?
mike